I think you're widely mistaken if you don't think Java is a platform. The VM and language are intertwined. The VM explicitly knows about things like records, language constructs, and idioms from Java. Java sets the direction of the VM, not Kotlin.
JVM does not know about Java, it knows about an IR that Java, Kotlin, Scala, Closure, Groovy, etc. all target. Java as a language also doesn't know about JVM, as it commonly targets things that are not the JVM, whether that is Dalvik, Graal or something else entirely.
That the JVM and IR has features to help the Java compiler generate better output is obvious but not really relevant. Modern CPUs also have instructions to help C compiles generate better code, but that doesn't make them C platforms. It's just that implementation details.
So no, Java is not a platform. It is a language that sometimes runs on the JVM together with many other large and quite influential languages.
