This is nuance that you and I neither misunderstand nor intentionally conflate. The election for President isn't a popular election, by design. It is NOT "one man, one vote".
It is one man, one vote, for POTUS, but with the restriction that the vote is at the state level, and that the electors of the state actually cast the vote for POTUS. I think we both understand that. So to say one man, one vote, is accurate enough.
Senate makeup is also not "one man, one vote", by design. It is, "one State, two votes."
Not since the 17th amendment. That's now, one man, one vote, within the jurisdiction. Each jurisdiction gets to elect 2 senators every 6 years in a first past the post ballot election.
So, yes: I would say that, "one man, one vote" is inaccurate - and that inaccuracy is a feature, not a bug.
I wouldn't correct anyone for saying it, because it is true in the above context. But also, I doubt most people who say it understand the context in which it is true.