Reread their last sentence.

What instance you use as your home instance is irrelevant unless it has been defederated from an unusual amount of instances. You likely don't want to try and use lemmygrad as your home lol.

Otherwise, home instance is only going to determine your local feed. Which is pretty much the least used feed anywhere other than maybe beehaw. Discovery via all combined with searches lets you populate your subscribed feed, so those are the ones that you'll use most.

Lemmy is federated by design. If you try and treat instances like some kind of dedicated site the way reddit was, you might as well not use it at all because you'll be missing out on the benefits federation brings to the format.

Are you old enough to remember geocities? It had these circles where individual sites within geocities would link to each other. You would have your own site, but be linked to maybe hundreds of others. That's closer to what lemmy is than the kind of reddit experience you're probably used to.