This is completely false. Not one shred of truth in it. The similarities between React and SwiftUI end at both being component-based UI libraries, just like plenty of others (Cocoa, Vue, Ember, Ext JS, Svelte, Qt, do I need to go on?—some of which provide various components out of the box, others of which don’t). Beyond that, they work in radically different ways and the way you will achieve things is radically different too. Just look at the avocado toast example and see how true this is.
AFAICT the way SwiftUI works is basically the same as React.
The way all of these frameworks differ from each other is both very slight in superficial details (think two-way binding or slots) and very, very strong in the basic implementation (i.e. the diffing or reconciliation algorithm).
So, yes, a lot of these look similar these days. But saying that they work the same is oversimplification in my opinion.
While it is heavily funded and used by Apple, I would never call it "proprietary". It's open source.
By that definition, C#, Go, Java are all proprietary.
https://github.com/ClojureTO/JS-Workshop
https://www.freecodecamp.org/news/a-realworld-comparison-of-...
SwiftUI is basically React implemented in Apple's proprietary language rather than a preprocessed JavaScript-XML hybrid [1]. More options is a good thing, but it hardly seems revolutionary.
[1] This works much better than it sounds like. I'm a long-term C/C++/Obj-C programmer and was very sceptical of JSX, but React is actually very nice to use. The toolchain is kind of byzantine but seems to be settling slowly on reasonable defaults.