Amusingly, propagate has a horticultural, and non-horticultural meaning, and it's not obvious which one you're using there, because the bee's role is long over by the time the seed is ready to go out into the world.

Pollen can be carried (as noted by sibling and you) by lots of different insects, and there's myriad solitary and other (by conventional standards) weird bee species around, plus lots of plants are happy to pollinate themselves (tomato is a good example) or rely on wind (corn/maize is the famous example there).

When the common honeybee landed in the continental USA, about four centuries ago, the same people also brought in lots of (other) european plant species that had co-existed with Apis mellifera for millennia.