I have used the same regulator for 12 years and decided it was a little long in the tooth so I bought a new one. Brass non adjustable on both counts.
The new one cut my water volume down to a trickle. Replaced the regulator with my old one and it was back to normal.
So yes, some regulators do have different flow characteristics. I bought a $12 water pressure gauge from Home Depot, it screws onto the end of a water hose and will be my tool from now on. I'll measure at the CG, if 60 or less no regulator, more, I'll regulate it.
Interestingly, my house at the outdoor spigot, pre regulator, is 100 PSI. My old regulator brings it down to 80 and my new one cuts it down to 40. I just got the gauge, if I remember I'll post my findings at various campgrounds.
Long and short, yes it could very well be your regulator. I was told that 60-65 was a safe max pressure for campers.
Rain Bird 3 in. P2A Water Pressure Gauge-P2A at The Home Depot