“Gaon: The point about how accepted Reb Moshe’s psak was is as simple as this: name one non-MO Rabbi TODAY who told you you can carry in Manhattan.”
Is Rav Henkin a MO?
Is Rav Zvi pesach Frank a MO?
Is Rav Yonoson Stief a MO?
Is Rav Weissmandel a MO?
In any case, the Manhattan eruv at the time did not consist of any Tzuras Hapesach, also, there were streets included in the eruv that were assumed to have 600K passerby’s in a day (there was actually a debate that being that shabbos/weekend there was no 600k, if you can rely that the “beChol Yom” quoted by the SHU”A needs to be literal, or at least on the very day in concern).
Said that, I’m sure there are many Non-MO who uphold that if the eruv is constructed of a Tzuras haPesach and does not include any streets of 600K, that you can rely on the eruv, especially, after Manhattan is encompassed with 4 Mechitzos Benei Adam..
Even Rav Moshe agreed (as per Igros Moshe) that there are certainly shitos you can rely on. (The only one that really came out strongly against it is Rav Ahron)
And why you won’t hear that many officially stating so, simply, just use your imagination…If you would to be a Rabbi that thinks it is muttar would you come out with a statement?