There’s no rules for the Fediverse, all it means is that they utilise the ActivityPub protocols to be able to federate with other websites that also use it (there’s others, but basically irrelevant now).
Mastodon requires OAuth2 for apps to get access to your account because it was designed that way, and Lemmy wasn’t, it’s as simple as that. Any platform can be part of the Fediverse (including Reddit, Twitter, Facebook etc if they really wanted to), which also means that platforms can also do anything they want.
I have worked in service/retail, and this argument doesn’t make a lot of sense. Most service/retail is actually 7-day weeks, but the workers average out to 5-day weeks with rotating shifts etc.
All that would have to happen is the workers now average out to 4-day weeks, with a similar level of pay (which is what the 4-day week advocates are asking for).
The 4-day week isn’t about office workers, it’s about everyone.