The root of the problem for Apple is that they cannot get away with doing what they used to in the past, they already have a plethora of platforms within their own umbrella to support, adding Windows native to the mix seems to result in maybe a handful of developers taking on enormous burdens by trying to catch up to their expected Mac apps.
If Apple were to seriously put its weight behind a cross-platform toolkit, this might change, especially as they want their services to grow. It's the very reason why their main service competitors can even compete.
But I agree that if they were to suddenly switch to Electron without a care it wouldn't turn out well, but likely have a better end user experience than their current reveals.
For Safari Windows they ported a portion of Cocoa.
Having an internal Windows version of SwiftUI would not be unthinkable!
No they weren't. They were notoriously awful. Apple resorted to bundling Safari with QuickTime to try to get you to use it but everyone still hated it.
I doubt they’d do much better using electron: I think their development model is that if it isn’t on one of their platforms, they pump out a minimum-effort, low quality app. I’d guess that electron ones would be just as clunky, except with a significantly higher memory and CPU footprint.