This is the dumbest article I've ever read.
First, Is A Real Boy is their second album, From Under the Cork Tree their third, and They're Only Chasing Safety their third, too. Full Collapse is sophomore. So half the list doesn't count right off the bat! (I'm too lazy to Wikipedia it... is Ocean Avenue a debut? I feel like "No.")
Second, either your album is good or not. Only simpletons decide a record is bad merely in comparison to another record. The Green album would've sucked had it come out before Pinkerton. Same with Louder Now...
As regards Underoath, specifically, all three post-TOCS albums are better than TOCS. Disambiguation was met with praise by critics across the board.
The articles title shouldve been more clear, but then again you should have read the actual article more thoroughly.
What he means by "debut" is an album that put said bands on the map so to speak or albums released at the peak of a bands popularity, more commonly their major label debuts. You should have been able to deduce this.