Still not valid. In MB we list the separated recordings. And a human ear can tell when there is a gap between tracks. We are documenting the music, not what a designer has created in the artwork. Common sense has to come into play. This is a Music database, not Artwork. (I assume ArtBrainz is a different project)
A sometimes useful thread is the Voting/Auto-editor Request Thread as that usually gets sensible eyes onto an edit.
I have come to accept that MB is not interested in mastering, and can see the logic in their definition of Recording. I’ll add mastering details in disambigs and annotations.
Don’t get me started 
. My Picard script just changes that to Worldwide as I really don’t care where Spotify operates. But I am mainly a CD\vinyl person so avoid it. (Just get confused by the different rules on digital media)
I see the value of even the most basic of editors. Even when they add only that track list, in all caps, with typos and no times. It is at least a start point and we can come along an upgrade their work. If people want to then fill in info that is irrelevant to me like ASINs - that’s fine. I doubt most editors care where their CDs are pressed, but I’ll still add that detail as it interests me.
I am digging through a similar size of storage of many TBs of music. In my case MB editing often triggers me to massively upgrade a whole catalogue for an artist I am interested in. Especially the lesser known one. That’s when I’ll pull in the other research from elsewhere and upgrade what I learn, and feed it back into the database. Share what I know. Adding links and quotes and references. Often I’ll have multiple sites open for researching back catalogues and I link as much as possible that I am reading. I treat MB as a central pool of knowledge.
It also causes me to go off EBay fishing for more albums to fill in gaps in both MB’s details and my collection. Far too often I have bought CDs just to get discIDs and track times.