You don't care what others believe.  You do the arithmetic.  If one rig is 1500 watts at 120 volts, then the arithmetic is easy.   1500 divided by 120 is 12.5 amps.  That means a receptacle (you did read the previous post) rated at 15 amps can only power one 1500 watt rig.  So one rig is powered by one receptacle and one circuit breaker.

Four breakers powering four receptacles means only four rigs - no more.  Again, never leave others to do your arithmetic.  You do the simple math.  Ask how to do that math.  Ask others to confirm your calculations.  Since only you (not even your electrician) is ultimately responsible for what happens.