Perhaps Nintendo are making such changes because even though the switch 2 won't be able to, maybe they're already thinking about a switch 3 or 4 and how it'll be able to boost fps that high in older backward compatible games?
A dataminer has found a reference to 240 Hz support in the latest version of the Switch engine. Whether the Switch will be technically capable of this is questionable. However, this compatibility could give the Switch successor a 40FPS/120 Hz mode.