I can't remember who exactly started doing it AND if it started way, way back than I and we all know.
Among the idol groups I followed, WINNER's the recent one I can remember with their single albums "Fate Number For" and "Our Twenty For" in 2017. BIGBANG also did it too way back in 2006 for their debut era (that was later done executed with TREASURE in 2020).
So who started, or re-started, the release of physical albums with only one to three songs at present times?