Maybe in Japan but that's not why they were doing it here.
Again, maybe in Japan but 99% of 1.5jz here are in MKIII's. 99% of those are are stock or close to it. Big cams, turbos or whatever they still make more power than a 2.5l 1jz with the same mods so I don't see your issue.
Another example. L6 heads don't flow much compared to alot of newer heads. Based on what you are saying about the head not having enough air for the added volume "it will make around the same power, but at a lower rpm. Sometimes it will make less power if the head is optimised for the higher revs of the smaller engine" an L stroker would produce the same or less power. Yet I have never heard of a stroker L6 motor making less power or the same regardless of how much lower it revved comparred to an an L24-L28 with stock bore and stroke. I know 7M heads don't flow well and they have a silly long stroke(91mm). Maybe if I destroked it I would make more power.