“As to why some argue excuses in the name of Rav Moshe that don’t follow his teshvos, I would say they don’t know his teshuvos that well. However, to claim that these arguments are Rav Moshe’s is simply not true, and definitely not possible, since Rav Moshe wrote otherwise”
Agreed. You either have to say the responsum in vol 5 has been tampered with or that the explanation was misquoted etc. There is no other way to go around it.