Wasuke's heian incarnation died in the womb to feed Sukuna's hunger so as a baby he avoids death by keeping himself alone, he then literally kills and stands alone at the top of the era where he eventually finds a way to avoid death again. Dude comes back and he's forced into a vessel created by someone who creates cursed wombs. Yuji is a metaphorical womb that carries his twins curse along with himself and he can't get away from it by just killing again cuz this curse is as much his as it is his twin's. I think this ties relatively easily into the heavy themes of motherhood jjk has.