Reb Moshe drank chalav stam thats a fact
It’s certainly possible that he did at some point, but he writes that he was personally makpid.
So far nobody has given me details to the story….
I happen to have heard that the story is true, but I didn’t even bother asking for details, because, really, what difference does it make?
We know that:
a) he held it was muttar
b) he was personally machmir, held it was better to be machmir, and even more so when it’s readily available.
So there’s no real nafka mina from the story. It’s interesting, because it shows the attitude we’re supposed to have towards maachalos assuros. If this was his reaction to unintentionally eating or drinking something which is muttar meikar hadin, how much more should we be careful of actual issur.
But it doesn’t change the halacha one way or another.