I have less awareness of where math rock is or isn’t today, but remember when it first appeared and what it refers to - generally intricate, technical, rhythmic-focused, largely instrumental rock music. It’s a bit less of a coherent “scene” than witch house was, and is/was more generally attached to a fairly broad range of bands albeit with some particular sound characteristics. I can kind of understand why the intricate, instrumental nature of it gained it the “math” tag.
The band Battles were one of the first to have the tag attached to them (see below). This album came out on Warp actually.
The band ‘Foals’ were also described as math rock pretty often in their early years. The similarity in sound to Battles is fairly apparent.
