In all honesty thinking about it it's probably not *that* impressive. That means it had a better May than the 3DS or Wii U had in the US, and 3DS was never really a juggernaut platform in the US, it was fairly rare to ever even see two 3DS games ever in the top 10 NPD at the same time. Wii U ... well uh we know how that went.
Um 90% is basically double, fyi.
Also as stated it does not include digital, which every year is increasing, so it likely is double.
As for last year. The switch had both BotW and Mario Kart 8 deluxe out for April NPD. Those are some big hitters.