Nirvana released Incesticide, a collection of rarities and B-sides, in December 1992. Many of Nirvana's radio sessions and unreleased early recordings were starting to circulate via trading circles and illegal bootlegs, so the album served to circumvent the bootleggers.[32] The album contained songs from previously released singles and EPs, including "Sliver" and "Dive", as well as material from the band's sessions for the BBC, including "Been a Son", "Aneurysm", and covers of songs by The Vaselines and Devo.
Thats some copypasta from wikipedia. Seems like a legit studio album to me.
Also Bleach and insecticide went platinum. An album does not have to be created in the studio in order to sound good and have a major release. For instance, all of the white stripes albums were recorded in their house.
Hoarmoaning does seem to be an EP with limited release, but discounting bleach and insecticide because they were not studio albums is unfair.