I don't understand how the market isn't considered big enough for any phone OEM: how can it be smaller than that of foldables? Or even if it is, isn't it still big enough, and shouldn't there generally be more sizes and form factors of phones?
It's as tho the car industry decided to only make 184" long SUVs (6.2-6.7" phones) and 200" long 3-row SUVs (foldables)... no other SUVs, no sedans/hatchbacks, no sports cars (much smaller and much lower volume). And different cars are actually hard to engineer and mass-manufacture the chassis and bodies for... in contrast a phone's HW is inherently more modular and mostly just the screen and battery need to be changed for each size.