I guess I'm not understanding the circumstance clearly, that might
lead someone to use that kind of information as an "OK to descend"
point.

When being vectored outside the FAF, ATC will say, "You're 4 miles
from x, turn left heading 210, maintain 2,500 until established,
cleared for the approach".

If you are between the IF and the FAF (as they said you were), then
the published altitude is 2,000. If you are outside the IF, the
published altitude remains 2,500.

If ATC says you're 4 miles outside the FAF, but you're really 4 miles
outside the IF, then if you descend based on that info, you've screwed
up.