Can’t speak for this case but it’s fairly common to use a lower capacity (250GB or so) SSD for your boot drive, Windows and commonly used programs and a high capacity (1TB+) HDD for your pictures, music files, documents, etc. Those files are small enough and accessed infrequently enough that there’s no real speed benefit to putting them on solid state storage and both drives might cost the same amount.
Except in this case, they’re both SSDs.
True enough. I still like keeping them on separate drives just for organizations sake and so a critical drive issue that requires a reformat doesn’t wipe out both my programs and documents. I wouldn’t have gone with an SSD for that (unless there was a case organization reason) but using two drives makes sense to me.