Oh, your still learning the teshuvos. But you argued in the name of Rav Moshe from the get go. If you never learnt the teshuvos, how could you have claimed to know what you are talking about? Clearly you are not capable of being modeh al haemes.
While I answered that one line twice, you have not answered the many lines that I cited.
From Rav Moshe’s words in this teshuvah (4:87) there is proof that Rav Moshe’s shitah was not static. You do not have a better answer for the fact that Rav Moshe himself wrote that he initially (in 1:139) only wanted to reckon those living in the 12 mil by 12 mil towards 600,000. The fact that only in this teshuvah (4:87) did Rav Moshe admit that eruvin were established in cities containing shishim ribo, is proof that his shita evolved. Clearly, one would need to learn 4:87-88, and 5:28-29, to comprehend Rav Moshe’s final thoughts on the matter, and the Manhattan teshuvah was not his last words on the matter.
“Anybody who actually knows how to learn,” would realize that you are in over your head. Stay out of matters that you know nothing about.