Uh, what?! Ys on Switch sold less than 1/5th of the Vita's first week.
He's probably refering to an insider's comment that Ys VIII's worldwide sales are in the same ballpark as the Vita version's worldwide sales.
A similar case is Disgaea 5 where the Switch version sold notably lower than the PS4 version in Japan, but sold similar numbers on a global basis. Disgaea 5's sales are confirmed by the publisher itself.