Current PTU setup is just a random first setup; we'll do a lot of adjusting and balancing before hitting live.
The plan is to have all mining zones worth for something (moons and belts), with proper hotspots and sometimes also hotspots with unique ores (like craters now on first moon). Moon mining has both area and depth-based veins, and in the future version also the "shell" ore will be based on location and/or depth. (like ice on poles, or ajatite layer at 2 km depth etc.)
Belts will get much larger and much more single-ore focused hotspot setups than what the current setups are.