To be fair, while there is invoke dynamic, he might be alluding to other aspects of the JVM (and referencing Parrot hints to that).
Eg. class loading in the JVM is (afaik) still static, classes once loaded cannot be modified, which is a problem for languages such as Ruby and JS, the basic data types of the JVM might not match your language, etc.
Not sure if that makes a big difference, in essence you'll have to implement those semantics in either case, be it in RPython for PyPy or Java for the JVM.
Eg. class loading in the JVM is (afaik) still static, classes once loaded cannot be modified, which is a problem for languages such as Ruby and JS, the basic data types of the JVM might not match your language, etc.
Not sure if that makes a big difference, in essence you'll have to implement those semantics in either case, be it in RPython for PyPy or Java for the JVM.