Correct, but again it depends on the setup. Prop companies around here will run 1/2 or smaller to the generator at a much higher pressure. I can't quote the exact pressure but I've accidentally connected my gauges to that side and the gauge broke instantly. Then at the generator a regulator is installed to step it down to 11-13 usually about 18 inches before it actually enters the generator.
There are more factors than "pipe size @ pipe length" that we currently don't know.
Pressure and volume can be tweaked relative to each other for the same final BTU output. Similar to being able to get roughly 3600 watts through a 14 gauge wire at 240 volts. If you drop that voltage down to 120, you now need 10 gauge wire to accomplish the same 3600 watts.
I've installed gas lines to 100+ gensets and figured ide add some useful info to the op of the thread. I wrote if supplying the gen for 20' with 1/2" pipe at 11-13"wc, it would be wrong. I didn't see anything stating it was a 2stg setup. Installing the second stage regulator 18" away from the generator inlet is also incorrect.