"Whatever GPM the engine uses with a (for example and easy math) 10 GPM pump, it will use the same GPM with a 12.5 GPM pump, which is a 25% increase."
This simply isn't correct in the real world, because it's too simple a statement. It ignores pressure, and it presumes the 10GPM pump was able to keep up with the demands of the engine in the first place.
The engine is built with an 'engineered' system. The pump and pickup are matched to the sump capacity and engine demand. Not always well matched, but nonetheless it's a system. When you go in and make one change to the system - such as a HV/HP pump, you can well upset the balance. The pump can now suck more, and the pan needs to have the capacity to support that sucking.
We can further see evidence of all this when the old trick of adding a quart of oil 'above full' stops the sucking dry problems. By adding sump capacity, we've alleviated the dry pan situation just enough to allow the pickup to stay covered.
I define a 'standard' pump as the pump that was used on the engine originally and (I guess) was engineered as part of a system.
