This may change vaguely soon, but right now you typically scale python apps by starting multiple python processes, while for Java you can just add threads. Python processes can't share a thread pool among all of them, while Java can.
Sadly, I’m deeply familiar. What made Evan Phoenix’s Rubinius work so exciting in ~2012 was getting rid of the GIL and seeing what was “fixed” by parallelism and what was not.
You make a good point. I didn’t read the parent comment that way but you’re right about how you scale python with the GIL vs JVM.