Why Noto Sans Mono is not considered as Monospace?

[beteunam-saram]

ecode said the selected font isn't flagged as monospace.

p/s: I downloaded from fonts.google.com so I don't think it's corrupted.

[SpartanJ]

Because many monospaced fonts are not actually "pure" monospaced fonts, most of their glyph will be monospaced but not all, so the font file won't be internally flagged as monospace when packaged, and ecode will not be able to take advantage of the fully monospaced font for coordinates calculation. It's not actually that problematic, the alert is slightly exaggerating the situation, I just simply don't recommend using non real monospaced fonts, but it will work just fine.