The body positive movement has been co-opted by so many companies now. Not only that, but it is not inclusive: it really only shows up to a certain size. Example: none of the men in that ad you posted are actually very fat. This is why I left it behind in favor of fat acceptance and body liberation. The body positive movement is not for me. It doesn’t make me feel seen.
As for whether it’s only for women, I don’t know. I think that maybe the wider movements of fat acceptance and body liberation would be more helpful to larger men who feel bad about their bodies. Either way, what’s really needed is change on a societal level. Whether or not you “care” about seeing different bodies, the fact remains that society as a whole views fat bodies as being bad and less than. That’s why we need these movements.