Omegaverse is still a fantasy trope though where the sexual oppression that exists is several layers removed from the real world. Eating disorders are very much real world issues.

Also, omegaverse is fairly popular, eating disorders popping up in fic when there's no canon basis for it is vanishingly rare. So omegaverse is much more in the "they should know it's not unlikely to appear and DNW it if they don't want it" than random eating disorder fic.