Confused, I went through similar agonizing about my ex's stated reasons for abandoning our r/s when it was in full flight & we seemed so happy. He said it was b/c we had radically different parenting styles (which we'd barely even discussed, & which I now know, after much subsequent discussion w/him, are very similar). After a little back & forth in the first throes of the breakup, when I pointed out he knew nothing about my parenting approach & I'd be flexible & open to his views, it morphed into how he just had realized he wasn't up for doing the kid thing again (my daughter was 6, & he had adult kids hed'd had when he was quite young).
So all this hurt me terribly. He'd known I was a single mom when he courted me & persuaded me to care about him & the idea of us as a couple. Now it wasn't worth the trouble of dealing w/my kid (who's great BTW

). I spent a couple awful months wondering if things would've been different if I didn't have a child, if I had a different child , if I were a different kind of parent.
Two months later, he wanted to know if we could talk. Spent 20 mins on the kid issues, & he felt they were satisfactorily addressed. Could we get back together? That didn't happen as he talked to his T who urged that he spend time learning to be alone, & he also seemed to get cold feet. But we stayed in touch for a bit till I realized he was pursuing his ex gf, a much younger woman whose requirement for a r/s was ... . having babies. Which would have required him reversing a vasectomy. Which he decided he would commit to doing. When I learned that (from mutual friends), it was a kick in the stomach & an enormous betrayal. He couldn't work out parenting style issues w/me but he'd promise to have babies with this other woman? Oh, I forgot to tell you that I was the love of his life, etc.
Point is--the kid thing w/me wasn't the real cause of the problem. I think HE sincerely thought it was, but the emotional cave-in he experienced was about how close we'd been, that we were discussing moving in together, but also, I was wrapped up in work emergencies & we didn't see each other much ... . lots of triggers. At the moment when things snapped, my kid was upset at something he'd done, I was comforting her--so that became the issue. But if I'd spent a ton of time trying to work that through w/him, I'd have been missing the actual problem, which is that he is scared of being so cloe to someone, a problem that is going to keep manifesting itself with different apparent "causes."
We're friends now & this happens all the time. He gets uncomfortable, pulls away, then points to some strange thing as the "cause." When we discuss the cause after his emotions have re-regulated, it always melts away. If I got focused on the stated reason & wound up about addressing it, again, I'd be missing the real cause, which is deeper but, it seems, invisible to him