Anyone, I repeat anyone who tells you to correct tire pressure for your rig without knowing wheel position weights (better) or at least axle weights is either:
Clairvoyant
Or
An idiot.
Not aware of any third explanation. The tire manufacturers have spent a lot time and effort to determine and publish load/PSI tables. There is a reason for them.
Yes, some coaches DO require full tire pressure to carry the load-- hopefully, yours do not (as lower PSI requirement also means that your tires have some safety reserve-- they are not maxed out).