Statistics only really work, if you have a reasonable amount of data at hand. Obviously it was easy for the Chess.com games to find the problematic games. But Niemann only played in 13 over-the-board tournaments.
Carlsen and another (anonymous) GM said some games were suspicious. For me, this is still more accurate than the statistics they used.
His very last video uploaded is called „I am Not Dead, I am 57 Today“. Approximately one month later, he died.