Reading through these comments and the numetal wiki, it seems my idea of what numetal is and what the world considers numetal are two incredibly different things. The wiki has Glassjaw listed as a numetal band. Disagree 100% on that one. Spiritbox? That's progressive metalcore if anything. Sleep Token? lol, no.
Numetal seems to have taken on a very broad subgenre role. Which, from what I know of music, it should sit (as it is defined) as a genre that uses basic metal music fused with other genres. Meaning it's never over-complicated and songs are written more like pop songs in their structure and simplicity.
Using numetal as a catch-all for anything that's a fusion of two or more genres is a bit, um, disrespectful to bands who are a far cry from just playing in 4/4 all the time with the song structure of intro/verse/chorus/verse/chorus/breakdown/chorus/outro.
They could be considered that, yes. Personally? Not really. It's just different vocal stylings on top of some regular ol' metal music. I'm not exactly versed on their music though so take that with a grain of salt.