I'm puzzled by the addition- of- regulator requirement for this unit- that's usually only true with outdoor propane
stoves etc., which operate at the higher
pressure of about 16"wc.
RV appliances are designed to work at about 11"wc pressure as supplied through the trailer's regulator, and usually don't come with a new one.
The only purpose of adding another regulator between this cooktop and the trailer tank would be to reduce the gas pressure to even lower levels. Maybe the regulator is just a redundancy supplied for ground-up installs?
I'd inquire about the cooktop's actual design pressure- if it's 11"wc you can leave out the new regulator.
But if it's higher than that (like an outdoor stove) it won't work properly on your trailer system.