Java primitives (short, float, double, etc...) are copied to the calling function, but arrays and objects are passed by reference. This is easier to explain in a language like C++, which can do either:

    // Java always does these:
    void f(Object& o) { ... } // passes objects by reference
    void g(double x) { ... }  // primitives are copied

    // Java can not do these:
    void p(Object o) { ... }  // copy of the object
    void q(double& x) { ... } // reference to primitive

CPython always passes by reference (pointer), and a C extension can break the rules and modify the otherwise immutable types (int, float, complex, string, etc...).

You can squint and say everything is pass-by-value because you can always pass pointers, but then we're really losing any meaningful definitions for what semantics we're describing. I mean, it's all pass-be-electron if you dive deeply enough.