alt Hacker NewsWell, this doesn't prevent the "flagship" app from shipping things and doesn't slow it down. So it's at least not slowing down development which is the argument the parent post was making.
I've actually observed the exact opposite thing. Since Bluesky is open source, it's often visible when developers start working on a feature. And they often check in lexicon changes early on. As a result, there's been a few cases where third party client actually added support for these features earlier than the official one since they already knew the shape of the data.
This wouldn't always work, of course. Yes, if you're developing an app or a client, you better keep up with the ecosystem. But the landscape is competitive and there is no cost to switching. So if something falls behind, you can use something else.
Moxie's argument is that even if something has a flagship app, this doesn't help because if you use a new feature and then your friend complains that they can't see what you posted, the experience is just that the flagship app itself is broken. People don't experience this as, oh well, my friend should just have picked a better client. They experience it as, that's annoying, the video feature doesn't work reliably on Y but it always does on X.
An extreme example of this is WhatsApp and emojis. WhatsApp doesn't use the operating system's text rendering APIs to draw emojis, instead Meta license the Apple emoji font and draw the characters themselves. That's because if you do emoji the standards based, open way you get these problems:
• People use visual puns that only make sense if emojis look a certain way, without realizing they might look very different to other people.
• People use new emoji, without realizing that old operating systems can't draw them.
The experience in both cases is that it's simply broken and buggy. Version skew can kill platforms, which is why the most successful platforms today restrict which clients can connect and forcibly expire them on a regular basis.
BTW I don't think it's worth generalizing from Bluesky. Bluesky is an X clone whose unique competitive advantage is censoring conservatives even more aggressively than Twitter itself once did. It has no technical edge so they can develop the site as open source without it being a concern to them - they don't care if they leak what they're doing because technical innovation isn't a part of their brand to begin with - and the AT protocol clearly doesn't matter to more than a tiny fraction of its users. The point you're making in the essay is general, but ends up feeling overfit to Bluesky.