Maybe it's just me, but the new disabled checkbox doesn't look disabled to me:
https://tools.wmflabs.org/styleguide/desktop/section-5.html

The normal convention for making a form element disabled is to make it faded out (<100% opacity), not giving it a gray fill.

I have no idea where this design came from or who is responsible for it, but I was wondering if the design team could revisit it.

Thanks!
Ryan Kaldari