Bees only poison you on normal and hard difficulty, you might have been on easy since it was able to sting you.
Were you on peaceful difficulty? Bees sting don't sting on difficulty.
I'm not sure this is a bug. I think the "Programmer Art" resource pack is not meant to change new items' textures, only the ones that existed prior to the new textures being introduced.
Bees only poison you on normal and hard difficulty, you might have been on easy since it was able to sting you.