Interesting view point. I've always seen a difference between a SONG and a TRACK, where a piece of music could be one song, but split into multiple tracks. This also explains why bands like DT have offered up SDOIT as 8 tracks, but also later as 1 on Score, since it was intended to be one song/piece of music, but indexed into 8 tracks for ease of play on the CD.
I usually go by what is presented on the album tracklisting and liner notes. If a piece is divided into parts and listed as such, like with Roman numerals (I., II.., etc.), but also split into multiple tracks, then I still consider it one piece, whether it's a song or a suite, like the multi-track suites on Chicago's second and third albums, or Pink Floyd's Ummagumma.
Denying a piece's status as a singular, cohesive entity just because it is indexed into multiple tracks seems a bit silly to me, but to each their own.
Think of it like a movie. Just like a suite can be comprised of many songs, a film is comprised of many scenes. You wouldn't call an entire film one scene (12 Angry Men notwithstanding ), so why call all of the songs in a suite the same song when it is really a group of songs that go together to form a bigger piece of music, ala Six Degrees..., Garden of Dreams or The Whirlwind.
Well, no, but in the analogy to films, a Song/Suite would be the whole film, and a Movement would be a Scene. If a suite or song is composed with the whole thing in mind, it probably shows in its composition and performance, regardless of whether or not the piece is indexed into separate tracks. Likewise, a film is usually written as a whole with a complete plot in mind. In both cases, their complete piece may not be recorded in order, and later be edited to fit together in its proper sequence but is still intended to be a singular work.
Now, if you have something like a Netflix miniseries, with an overarching plot but individual episodes, I'd liken that to a concept album like SFAM or TDSOTM, with ideas presented separately but working for the whole thing, rather than a whole thing with individual movements. Does that make sense? If not, I blame my tiredness.
As for indexing them as one track on a live release, A Mind Beside Itself was done that way on Live Scenes..., yet almost no one calls that one single song anymore (I used to, but I have changed my opinion over the years on how I see these things). Had DT recorded the entire 12-step suite live with Portnoy still in the band, I would imagine it would have been indexed on a live DVD as a single track. Pure speculation on that one, but I suspect that would have been the case.
In the case of the 12SS, I imagine it would have either been 1 track or 12, but probably most like as 5 since the individual songs are more recognized that way.
-Marc