"Fleetwood Mac In Chicago" - Not A Regular Studio Album?

[cbBen]

I used to play it when I was a college radio DJ (not the "Blues Jam" but the one titled "Fleetwood Mac In Chicago"). And as I recall, it was a regular album, not a compilation, so why does Wikipedia list it as a compilation?:
https://en.wikipedia.org/wiki/Fleetwood_Mac_in_Chicago

As you can see from the entry, it's all from the same studio session. Wouldn't that contradict the notion that it's a compilation?

I do have one admittedly off-the-wall theory: Christine isn't on it, and there's an odd desire on someone's part (maybe just whoever does the Wikipedia page) to say that she participated on every Fleetwood Mac studio album after the first one.

But there must be a more coherent answer as to why this is not listed as a proper studio album.

P.S. It's weird that the official Fleetwood Mac website doesn't include a discography.