What are Bento bones, and why do they make some products incompatible?
Bento added extra bones (wings, tail, hind limbs, fingers, face) to the shared avatar skeleton. Products rig animations to those spare bones, and each bone can only be driven by one animation at a time, so two items using the same bones conflict.
What Bento is
Bento (Project Bento, 2016) upgraded the standard Second Life avatar skeleton with about 106 extra bones: detailed face bones, bones for all ten fingers, extra spine joints, and three whole spare limb chains: a wing chain (10 bones), a tail chain (6 bones), and a hind-limb chain (9 bones).
Every avatar in Second Life shares this same skeleton, so those extra chains double as "spare joints" any creator can rig to.
Why products use them
The base skeleton only has one set of human joints. To animate non-human extras (flapping wings, swaying tails, twitching ears) or to build poses that need more joints than the body has, creators rig their mesh or animations to those spare chains instead. For example, the Crawling Doll Suit's thrusting toy is animated on the wing-bone chain. The crawling poses themselves are ordinary animations; it's the toy that needs the Bento bones.
Why that causes incompatibility
A bone can only be driven by one animation at a time. If your avatar already wears Bento wings rigged to the wing bones, and a product's poses animate those same bones, the two fight over them and the result glitches. That is why the Crawling Doll Suit and similar products list Bento wings as incompatible: nothing is broken, the bones are just already taken.