Still don't understand static files

[David Burke]

/static/grappelli/js/admin/DateTimeShortcuts.js

In dev this file (from SWoRD git) should contain lots of stuff from the old Admin interface calendar widget. 

In production even with a fresh collect static we have it as a blank file from Grappelli. They don't use it and just leave it blank. I just manually changed this for now.

So why in dev does do site wide static files take precedence but on production it is reversed. In most cases site wide stuff always is priority 1. For example templates for the site 

/templates

overrides all apps (app_name/templates). I can't find any documentation on django static files on what takes precedence. It's so odd it would reverse itself based on dev vs production!