Can someone help me understand what Core Miner resource drain?

There doesn't seem to be any effect when I replace a normal core miner with a rare core miner. The alt-click window shows that a rare core miner should have 66% resource drain, what does that mean exactly?

My normal core miner shows 11 core/s
My rare core miner shows 11 core/s

It is useless stat, since core mining does not mine a finite resource. You would need another mod to make use of quality core miners. For example there here are some mods for train speed and capacity but the quality mod does not change those in any way.