Except the difference is between an album (like 2112 or Aqualung) that clearly isn't a concept album, compared to albums that could conceivably be called concept albums (Sgt Pepper, DSOTM, or Power Windows, for example) that I think is a pretty clear boundary of when the term "concept album" can be used or not (i.e. the story/theme/concept runs through the whole album). If there's a set line in when something can be called a concept album or not, that seems to be the best and most literal definition IMO. 2112 was just mentioned because every article about Rush ever calls it a concept album when, in Ian Anderson's words, "a few songs does not a concept album make." Also, trying to split up concept album discussion into "rock operas," "thematic albums," etc. is when things get anal and unnecessary. You can refer to certain albums as such, sure, but there's no need to call Tommy a "rock opera" INSTEAD of a concept album, if that makes sense. That's what my whole bullet point there was referring to.
Also, its pretty ironic that you're probably the one person on this board who is/was the biggest stick in the mud about that kind of terminology on this forum and you're calling me out.