It was just an offhanded comment about the 23s you mention.
USAF never got any MiG-25s, at least not for keeps.....just one pilot.
And realistically of course, those high Machs achievable by a number of fighters at high altitude have limited practical use. After a long fuel burning climb, the run from 1.1 or so to 2.0 in a clean F-4 took somewhere around roughly 5-6 minutes in AB on a good day, and 100+ miles of non-maneuvering flight, and resulted in about half the fuel remaining that you started the run with. With this amount of fuel left you'd better be reasonably close to an airfield....or a tanker.