Nature kinda beats you to it, except we're talking about a baby bug instead of an adult one.
Caterpillars. Few people are unaware about them, their drastic metamorphosis and their diet that is usually centered around leaves. The thing is: a bigger number of people is unaware of the "usually" part.
The stick looking creature in the picture (by national geographic wild, video present in the following link) is a hawaiian carnivorous caterpillar, a baby moth that evolved out of their vegetarian diet to become a praying mantis-esque predator. Their hunting strategy is pretty simple: find a branch or leaf, camouflage as a part of said branch or leaf and wait until prey triggers the sensitive hairs at the rear part of its body, at which point it'll swing around and use its strong spiked pincer-like legs to grab a hold of and potentially stab prey, going back to its straightened position before enjoying the spoils of the hunt (in addition to the previous link, you can also see their attack method in this video).
Now, 2 key differences between a swinger and this nightmarish caterpillar are that the swinger is much larger, uses its mass to actually stun prey through a direct hit and then eat it through large bites with slightly different mouthparts. The caterpillar on the other hand swings simply to reach the place it knows the prey is, instead relying on its mass, it uses sharp claws in its limbs to grab a hold of and presumably stab prey in order to kill it and eat.
Also, here's one of this caterpillars (image found here) compared to a replica of an English medieval Mace and see how they can be fairly similar to both maces and Mace-shaped animals :
So essentially, is it possible? Clearly yes, to an extent at the very least (except maybe for the spiral mandibles and feeding method, because arthropods are a group with very varied mouthparts, yet I've never heard of carnivorous insects with spiral mouthparts, especially when a classic "scissor" design does the job just fine. Not impossible, just a bit improbable. As for the feeding: eating very large chunks out of anything, as snakes might hint, drastically hinders digestion and requires a pretty damn big/stretchy mouth and a fairly linear digestive track, so taking it easy and biting off smaller chunks also sounds a bit more realistic and energy efficient) , at least in a smaller scale.
The main changes we need to do to this caterpillar to become almost exactly like the swinger (at least in regards to their overall hunting strategy, because none of the predatory arthropods that hunt by ambushing prey that I know of are closer in overall shape and method to a swinger than this one type of caterpillar) are size and power, both of which can be done through magic (because realistically increasing the size of arthropods is quite the can of worms, and because magic allows us to ensure they can still perform the super feats that would normally be only possible thanks to their small size). With these changes alone, we could have a creature that camouflage as a thick branch of a tree or even as a small dead tree on the ground, which will pounce at any small creature that comes close enough to its base, slamming the creature down and piercing it with its 3 pairs of knife-like claws, only to calmly stretch back up and calmly eat its meal. Just with these alone we already have a creature capable of striking from above by swinging down on its victim, except that instead of a recking ball swing it's more like being slammed by a piano with 6 knives attached to its bottom region. Special long hairs a little closer to the front of its body could also help sizing prey (if they're triggered when the animal is passing by, the prey might be too big and attacking it might be risky).
As for how to give the final step towards making them into true swingers with a wrecking ball motion, we could potentially make their thin sensory hairs longer and retractable (but watching out to ensure they aren't too frail or at least that they can grow back quickly enough if broken). This way we can have the creature on the ceiling attacking anything below, with the length of the hairs potentially still allowing them some ability to select prey by size (if the creature is too small, it won't be detected, and if it's too tall the caterpillar could potentially receive a stronger signal since the hair is getting triggered more violently and closer to the base).
This kind of shows how keeping your base on the ground and pretending to be a small tree or a thick branch can help them with finding prey, since an arboreal environment already limits the size of animals and the act of keeping your base on the same place animals are walking means you can be sure when something is below, since you can know if something did or didn't touch your....butt? Still it might not be impossible to allow them to anchor themselves above, swinging down and slamming their frontal region onto prey and yet again using their fierce claws to hold onto and stab its next meal.
"but wait, if they're giant caterpillars, what do they turn into?". Well if they remain at the max length of a Mace, I can't really be sure, but if they grow a bit larger, they might even fit the role of larval stage for a certain kind of moth you've asked about before (although allowing them to grow allows them to hunt bigger game, which, according to a certain webtoon is very bad for whatever creatures unfortunate enough to become a part of the new menu).
EDIT: your swingers are apparently very merciful predators when compared to the bugs they could've evolved from. It's not just that I couldn't find whether they truly do kill prey by stabbing it with their claws or not, it's just that these caterpillars usually don't bother to kill or even stun their prey before starting to dig into it.
