The ones in /proc/cpuinfo are cooked values anyway; there is plenty of history to that effect.
I don't know this history. And I don't care.
I thought /proc/cpuinfo should show an (almost) complete list
of CPU features. If this is not the case it's a pity.
I would agree with Andi that if as far as Linux is concerned mwait is unusable on AMD Fam10 processors, then the CPU detection code should turn this bit off on AMD Fam10 processors.
And finally I was not aware that you and Andi think of monitor/mwait
as a synonym for Intel's native C-States.
So I guess, what you really want is that for AMD CPUs the
monitor-flag (aka native C-state-flag) gets removed.
And if somedays another use case for monitor/mwait appears, the flag
has to be reintroduced for AMD CPUs.
Fine with me.
The only drawback is that Andi's idea of idle=mwait wouldn't make
sense anymore.