I suppose there is little enough left to say beyond the conclusion that must seem both obvious and (I hope?) inevitable. If you see holding out as akin to de facto parentage–two paths to claiming parentage by actually performing the job–then how can you justify two different standards for attaining the status? It’s one thing to understand it historically, it’s quite another to justify it as a continuing state of affairs.
Even more specifically, if you have a presumption of parentage by virtue of holding out, how can it be available to men only? The only possibly rationale I can see would be that you cannot reasonably expect men to meet the higher standard of de facto parentage. But that’s an argument I wouldn’t even attempt. It does a disservice (to say the least) to men and it embeds deep assumptions of gendered parenting in the law. Surely it would be preferable to have only one standard that would uniformly be applied to men and women claiming parental status by virtue of having acted like a parent.
That would raise the question of what the single standard should be. I won’t yet attempt an answer to that. (This would loop me back to the discussion I started here, I think.) But here are a couple of preliminary observations. If too few bread-winning parents (who may often, but not always, be fathers) gain recognition under the de facto test, then perhaps the test isn’t calibrated correctly. Perhaps it needs to take into account and recognize the possible division of labor that makes one person a primary breadwinner and the other a primary caretaker in a household. Or perhaps it shouldn’t take that into account. But at least the question should be squarely addressed. Similarly, if too many people might be able to claim parentage under holding out, then perhaps that means the test is too easy. Again, something to consider.
Finally, before I move off from here, there’s an important structural point. The holding out provisions are in the UPA which is a model statute. Statutes are considered and enacted by elected legislators. The de facto parent doctrine is a judge-made common-law doctrine responding to the equities of specific situations. Thus, these two parallel routes have become part of the law in different ways. I’m not sure there’s a grand conclusion to be drawn there, but perhaps it is worthy of note.