Pashuteh Yid – though I still strongly disagree with you as far your application to non-jews (more on that later) – I believe your reading of R’ Moshe is the correct one, and I have reason to conjecture that this was his reasoning as well. R’ Moshe was not known for being unsure of himself. V’Dai L’Chachikima.
I find it interesting that SJS’s posek was mechalek between jews & non-jews – again, I suppose to machmir in an issue of yeharog v’al yaavor and being lenient when it’s not and relying on Rov, I suppose. Interesting (but very valid).
And can we drop the issue of tehora? It’s inappropriate. And totally irrelevant (eshes ish is ervah 24/7).