Re. [1]: ppc64 on macOS was always an afterthought. It was only available on G5 systems, so developers couldn't ever rely on it being available, since the Power

Re. [1]: ppc64 on macOS was always an afterthought. It was only available on G5 systems, so developers couldn't ever rely on it being available, since the Powerbook and Mac Mini were G4 to the bitter end. And, as you mention, there was a long period where the GUI libraries weren't available for ppc64 (probably because they depended on 32-bit Carbon on the back end), so using it required developers to run 64-bit code in a separate process. From what I recall, the performance benefits weren't even that dramatic (and were only available on the G5 which was already pretty fast for the time), so very few developers bothered building for ppc64 unless they really needed the larger address space.