That has been going on in the greater metal scene for a long time. Especially for smaller artists, they put out a bunch of demos and EPs before putting together an album. In contrast to what you're mentioning, often the main tracks of some of the EPs will be on the album, but all of the "b-sides" will only be available on the EPs, but I've also seen examples of multiple EPs being re-released together. Not necessarily as an album in the traditional sense, but as a compilation.