A few comments...
Resolution-agnostic fonts. This has been a part of Macs since their inception [...]
Mac's "inception" was 1984 and, no, fonts were not resolution-agnostic.
Apple developed Postscript based on the same concept.
Adobe developed Postscript and worked with NeXT to develop Display Postscript. Apple had their own technology for fonts as part QuickDraw GX, which went nowhere.
iOS relies on a fixed resolution.
I'll admit, I'm not up on the latest for iOS. But last I looked, iOS now has support for variable resolution. But you're right that it didn't initially.