It would still hold back their handheld games though (especially on NX), since they'll need to take mobile constraints into consideration.
They are talking about handheld games, which are mostly stuff that is tightly budgeted. Games like I am Setsuna and to a lesser extent World of Final Fantasy.
You are not going to see Dragon Quest XI on mobile. Or Dragon Quest Heroes 3. Or Kingdom Hearts 3. Even if those games are released on the NX. (Not saying those 3 games are going to have a NX version)
But then you have stuff like I am Setsuna, World of Final Fantasy, DQxFF Fortune Street and the likes, which have a Vita and PS4 versions. Those games are more tightly budgeted. And WoFF looks amazing, but it's a rather simple game tech wise.
At some point, you are not going to be held back by the Vita, or Android, or whatever, but the fact that in Japan developers create games that only need to sell 100, 200 or 300k units to break even.