Total oil flow in any engine is the combination of all the internal leaks. Once you supply all the leaks, the oil pump can’t force any more oil through the system and you start to get pressure, which is resistance to flow.
The only way a pump can suck the pan dry is if the pan is too small to start with for the oil flow through the engine, the pick up is too far from the floor of the pan (which really isn’t sucking the pan dry but the result is the same), the oil is trapped in the engine and cant back to the sump.
As pishta pointed out, windage trays and crank scrapers are a huge help. Pan design is a big deal as well.
I had a customer who calculated his engine’s oil flow. He needed 10 quarts in the pan to run 170 plus MPH and end up with a quart in the pan at the end of run. He purposefully made the heads trap oil so it wasn’t falling back on the crank. He had little margin for error, but when you are trying to set a National Record that’s the kind of stuff you do. And the rules said wet sump only or he’d have used a dry sump.
