Why does the Metroidvania genre refer to Symphony of the night, rather than Simon's quest? [closed]

Based on the Wikipedia definition, the Metroidvania genre has roots in the Metroid and Castlevania series/games.

Metroidvania is a subgenre of the action-adventure genre of video games. The term itself is a portmanteau of the series' Metroid and Castlevania. Specifically, the term derives from the Castlevania title, Castlevania: Symphony of the Night, of which is generally considered to contain certain aspects of gameplay comparable to that of the Metroid series of games. As such, the term is used to invoke gameplay concepts and mechanics similar to that of these two series. The portmanteau "Castletroid" is also used to described the genre, albeit less frequently.

While the Metroid genealogy is obvious, the Castlevania part puzzles me. Why does it refer to Symphony of the night, if the main gameplay elements defining the genre were laid in Simon's quest (and Metroid)?

Did SOTN introduce something new that I miss, that clearly defines the genre?

Note that with the context of Castlevania, I refer exclusively to Simon's quest and Symphony of the night; it's implied that the other games preceding SOTN were side-scrolling platformers.