He be wrong then! But admittedly, they are close relatives. There are 2 stories related to the emergence of the Maine Coon - one involves some unlikely guff to do with shagging racoons (hence 2nd part of the name). The other goes that Marie Antoinette planned to flee to America and sent some of her favourite NFCs (wot she had got from some Euro suck-up that she had met) ahead of her. Every plan has its flaw and MA didn't make it but the cats did and interbred with the local (either wild or to some extent domeseticated) cats to produce the Maine Coon.
Whatever the real story was, there is no doubt that the MCs are very closely related to both the NFCs and the Siberians. I expect someone from Svartalfheims will be a long in due course to provide far more reliable info than me. This is just the stuff I came across while researching proir to taking Dot.
C.