As someone who Had a Nintendo DS and 3DS it certainly seems like a cool idea but they also had the problem of the hinges breaking rendering them useless, this is much worse on the folding phones where the display itself bends in half and can literally wear out just from opening and closing, rendering the phone next to useless, the DS handheld gaming systems didn’t even have that problem.
For that reason I really don’t like them and can’t really get behind them. I prefer my devices to last to obsolescence (a ripe old age) and be durable, folding screen phones are not that whatsoever. If I wanted a bigger screen I’d rather just have a bigger phone honestly, or be able to dock it in a laptop like enclosure.