Feif Un,
It certainly was R’ Moshe’s opinion; this was, as I mentioned, publicized years ago and R’ Forst merely reprinted it.
In all of the teshuvos in Igros, reference was made to the preference to be machmir, but this one is even clearer. The one in the (controversial) eighth chelek is also quite clear. I’ll copy the relevant passage from earlier in the thread (emphasis mine, parenthetical notes removed):
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