The good doctor himself, Dr. Kawashima, has been featured in an interview on Nintendo's official Japanese website. They had Dr. Kawashima come in and give Dr. Kawashima's Brain Training for Switch a shot, and also talked to him about his gaming outside of his own series of titles.
Turns out Dr. Kawashima is quite the Switch fan! He says he's mastered all the shrines in The Legend of Zelda: Breath of the Wild, and has recently started playing Splatoon 2. He also played and finished The Legend of Zelda: Link's Awakening, which took him roughly 3 weeks to complete.