> the barb doesn’t stick in other organisms

I don't think it disproves "honeybee barbs are adaptive against mammals", for example:

1. It may not be adaptive for honeybees to self-sacrifice against smaller targets. The full venom dose could be overkill, or it may be better to have multiple tries or engage multiple foes.

2. Perhaps it's just harder to evolve a good barb against smaller targets or ones with different surfaces/material.

3. Would smaller/different barbs increase the risk of damaging "accidents"?

It seems safe to assume there are evolutionary pressures around stinger-design, especially when we consider that queens of the same species do not have the same barbs.