COMG has been very PS-leaning for a long time now, it's numbers on Switch games aren't a reliable of the wider demand at all.
Very much untrue. Compare the actual sales of Days Gone and Sword Art Online: Hollow Realization (Switch version) with their COMG points for instance.
The audience that a game is targeting is what matters more than the platform. A game that targets the otaku audience (as SAO does) is much more likely to be overestimated and a game that targets the casual audience (like the Yokai Watch series) is much more likely to be underestimated.
The reason that it can be perceived to be PS-leaning is because PlayStation has a lot more games aimed at otaku on it and the Switch has a lot more games aimed at a casual audience on it.