Right, they're the same because it's a single bit. You 'and' with a mask to get the bits you want, and you 'or' together the values. It's an old habit left over from my bit-twiddling days.

I guess the test could really be:

have_fmt_spec = (oparg & FVS_MASK) == FVS_HAVE_SPEC;

to make it more clear what I'm doing.

It's easier to see the same thing with the FVC_MASK and FVC_* values, since that field is multiple bits.