Kotlin’s reified generics are pretty limited — they only work in inlinable situations, as there is no JVM support.

I assume that Kotlin will quickly add proper reified generics support as soon as the JVM allows.

(Your link above is about reified generics in the JVM, not just the Java language. Which is great news.)

It can't, because Android uses its own stack and ART will surely not be compatible with whatever comes out of Valhalla.

Then there are the JS and native backends as well.

So at best it will have to make use of KMM, and you will get classes with very different performance behaviours depending on the target runtime.