I have not yet reviewed the code, but the federated instances should be equally as functional as the main instance. However, having the option of functionality does not mean that they will operate the same way.
Your parent is not making a technical claim, but a social one: that there will be instances that are effectively unmoderated, because the people who run it hold that up as some kind of ideal, and that that is a problem.
I do not share this opinion personally, but have seen many people express it, so I feel like I am representing it accurately.
In fact, I would go so far as to say that it's incorrect, and not just an opinion, because unlike in Mastodon, moderation is not tied to your instance. Of course, whoever owns an instance can decide to kick someone off of it, but that's not the primary moderation mechanism in BlueSky, which allows you to choose your own set of moderation tools, regardless of which instance you or anyone else belongs to. I linked to the main three posts to understand BlueSky's moderation stances and features upthread: https://news.ycombinator.com/item?id=39471973