Here's another one.
Jordan's "Notes on a Dream" album. Specifically the tracks that he originally contributed to... are those considered covers?
There are covers and originals.
So many of those songs are from pre-Jordan DT and some are Jordan-era DT.
If you were to say, "Jordan released an album of covers and some originals" it would imply that some are, ya know, original. (So I just looked, apparently there are 3 originals which are classified as such because they've never been done before).
Then you find out some of the songs are interpretations of songs that were written and recorded with him in the band. So, The Answer Lies Within is on that album. When it was first released, it went through the DT ringer. People changed bits and pieces, James added his voice, Portnoy probably gave a direction like, "Let's make this like Radiohead meets Lady Gaga meets Los Lobos" and then it was released as the band Dream Theater.
Jordan then records it and it is declared a "Jordan Rudess song" because he didn't get any input from the rest of the band, some of them may never have even heard it, and calling it a cover differentiates that and the already established version.
Also, calling it a cover doesn't necessarily de-legitimize the song but it does help give it context.
With the Therapy? analogy, it clearly gets muddy with who is in the band at what time and whatever or if it's just a guest appearance. For the sake discussing the music industry, I think it is just more clear cut and easier to discuss.