as simple as ^^
What about changing the role you have been in previously? I have worked in data infrastructure previously but done ML coursework in grad school- can I pick a ML based team?
Yes, you pick. One of the cool things about Facebook. And it definitely doesnt have to be what you did before.
What about when the offer was for a specific team as a PM? Do you still go through the boot camp?
Mutual selection. Sometimes the team rejects you too, but not quite normal.
You pick.