Why do the guidelines for Release Group-URL "Official homepage" say that "It should not be just a sub-section of the artist's site"?

First of all, what is the distinction between a "separate website" and a "sub-section"? Is it a matter of consisting of multiple pages rather than all being readable by scrolling? Of having a unique design that sets it apart visually? Is it supposed to be something about the domain name that it's hosted on, or whether the artist's main website links to it or not?

Maybe more importantly: if an artist has an informative page about the creation of a specific album, why would we only want it to be associated if it's.... whatever the criterion for a "separate website" is? What's the intention behind wanting users to have to click from the release group to the artist's entry, then to the artist's homepage, then to browse around the artist's homepage to find a page concerning the album that they were looking at on MusicBrainz? (If that's desired, why allow linking to specific pages on sites like Discogs, rather than suggesting they visit the Discogs homepage and browse from there?)

I see that there's a Release-URL relationship for "discography entry", but that doesn't seem appropriate either: for one thing, the page might be discussing the album in general (i.e. the release GROUP) rather than the creation of a specific release of it (I wouldn't expect to find a page saying only "here's what it was like making the audiocassette version of our famous album"), so a Release-URL relationship doesn't seem like the place to put it; for another thing, if the website doesn't also contain a page discussing EVERY album the artist has made, then does it count as an entry in a "discography"?

(For the record, I had previously been putting these types of links under "official homepage", until I came across one whose URL was more than one directory beneath the root, and discovered that the MusicBrainz website was truncating the URL for what seemed like no reason, until I dug into the docs...)