Any libraries in the Maven repos that rely on JNI have to include platform-specific native libraries for each platform. For example, anything that uses Unix-domain sockets, which weren't supported in Java until this very release.
There's no portability requirement to being on Maven Central. Maven Central regularly hosts non-portable bytecode - like every AndroidX library.
And, again, none of those libraries run on Windows, Android, iOS, and web - the 4 major platforms by market share. At best you get half of those, but typically you don't even get that, and that's still only libraries. None of them are portable applications.
It's trivial to write semi-portable C++ snippets, too, that's not a major achievement.
Now you're being intentionally obtuse and moving the goal posts from your original claims just to score points.
You're not arguing in good faith.
Feel free to stick with your invalid views on portability, the rest of us JVM developers will keep enjoying the portability that this wonderful technology provides us.
There are gigs of JVM bytecodes stored on Maven Central and these bytecodes are being downloaded and run on macOS, Windows, Linux, and Android on a daily basis without a single change. The very same libraries. Unchanged.
That's the very definition of portability.
I don't understand why you keep shifting topics by bringing up irrelevant observations.