It's not that dissimilar to how Dioxus does this kind of thing with rsx! but yeah, it first got released in 0.19 and got big improvements in this release. It'll be interesting to see how uptake and adoption goes.
Dioxus is much easier to understand though, and Leptos and Yew are just HTML. One of the core issues is that (a) a scene format for editors, (b) a SwiftUI-like DSL for UI, and (c) a DSL for spawning game objects are just different problems. A single syntax that tries to cover all three ends up being a compromise that satisfies few.