So let me get this right...
The Mastodon app is no defaulting to mastodon.social so that when people join they aren't confused and can decide to switch instances if they choose.
Which, let's be honest, most wont.
I get trying to play to peoples expectations. People expect Mastodon to be like Twitter because that's what everyone compares it to, and when they are asked to select an instance, their brains glitch and they become disinterested.
Will this work? I don't know. Time will tell.
You may have a good point there, perhaps we need to start a campaign to get mastodon added to some basic IT courses, or rather get them to teach Mastodon rather than twitter.