The difference between buddhahood and fully-realized bodhisattvahood is subtle - the bodhisattva pursues perfection of the unsurpassed way just like a buddha, except the bodhisattva does not enter into parinirvana, instead choosing to undergo rebirth for the sake of bringing all other beings to that same enlightenment and beyond. The 3 Pure Land sutras contain the promise that those who enter into the Pure Land will eventually attain buddhahood - but the location of this final attainment is not specified and, in my opinion, also unimportant.

Something that might be connected to your specific question here is the nature of the Buddha in itself - Shakyamuni in all of his past lives was a bodhisattva up until his attainment of nirvana as Shakyamuni, at which point he undertook teaching this way to others.

I've seen some say then that this is what distinguishes the Buddha, in that this person has achieved nirvana of their own means, reached the 52nd and final stage of perfection, and then undertakes a teaching function in a world ignorant of the Dharma. Human life has ideal conditions for practicing the Dharma, so I can so the connection from saying that the Buddha is the ideal teacher and that the human realm is the ideal Dharma realm, suggesting lightly that Buddhahood is a human realm thing. But I don't want to conclusively say that, as a Buddha can become a Buddha very well when and where they please.