Oil pressure

Yep. Run a pump faster, it pumps harder, pressure goes up.

Now, the real question is how high and how low does it go? Going too low can be a bad thing.
 
But....I had a Bronco with a spent 351. Cruise at 40 psi, let off the gas and cruise down hll at the same speed and the O/P dropped to 10. Theory was the crank was walking back and forth so bad from bad bearings or a bad thrust the clearances grew big and the OP dropped as it did.