I would only take this article seriously if you have to support old iOS versions.

NavigationStack has been around since iOS 16, @Observable since iOS 17. and I'm not sure if the author is aware that GeometryReader hasn't been necessary since iOS 18 added onGeometryChange modifiers. Nearly 100% of users are on iOS 16+.

I'm doing some fairly complex work with SwiftUI and I find most components work identically between iPad and macOS. I can work for a week without needing to test on an iPad.

There are problems with SwiftUI for sure: I'm finding macOS performance on an M2 Max is far worse than an iPad M1, especially with animations. Toolbars are very inconsistent between platforms and the compiler timeouts are a real pain (hopefully Swift 6.4 will fix that).