Does Firefox support canonical decompositions?

https://github.com/notofonts/latin-greek-cyrillic/issues/449#issuecomment-2000946699 states:

The font does not have , but has = and ̸, which are canonically equivalent, so browsers like Chrome, Edge, etc. use them instead of falling back to ad different font, while Firefox doesn’t use canonical decompositions.

The font should either support , or make = and ̸ render correctly.

This appears to be a rather significant feature-set lack. Consequently:

  1. Is this true?
  2. If so, does a Bugzilla issue track its implementation?
  3. If not, why not?