> a) A 30 sec - 10 minute process to build (vs 0 in python)

Have you ever run someone else's python code? You have the exact same issue pulling down their requirements.txt, which is often not enough because you need to apt-get other libraries, try pip again, apt-get more, try pip again, etc.

> b) Weird because Java has a fatjar concept.

Sure, that's what you would do if you wanted to deploy an application to proc, my point was that it supports the same git checkout workflow if you want it to, which can be useful when dealing with other people's code and you want to make changes and not just run whatever jar they made.