There are come options. First, people tend to want to pick a bigger motor for longevity. In reality, the motor amp draw is based mostly on load applied to it and not the size of the motor. But when calculating loads, you typically use the motor HP number in the code book to determine load. So if these motors are oversized, the price you pay is a higher electrical service rating and larger branch circuits.
Next, with the VFD, maybe it needs to run at max power for a short time so they bought properly sized motors. If all the motors need to run at max power, even for a short time, then the load calc should be the sum of all motors. Some places in the NEC let you apply a diversity factor if you have a bunch of something (e.g. stoves, clothes dryers, etc) and not all run at the same time. But I don't think they tend to have that for an array of pumps.
Finally, if this is an existing service, you can do a load calc based on actual measured KWHr readings per 220.87. This is easiest if you have a smart utility meter and they show your peak usage in the 15 minute intervals specified in the code book. The problem is, if these are new motors being installed, you have no usage history. It could still help your calc in that all existing stuff could be arm waved into a measured loading instead of the excessive number the NEC calc provides, then add you new pumps. Or maybe you can install some of them on the existing infrastructure to see what their actual loading will be? This could be a slow process, as you need 30 days of usage data if you follow the exception process in 220.87, then add more pumps and do it again, and repeat until they are all in.
If your service rating is already near the measured demand, you probably have no choice but to upgrade. If this is a new service you may be stuck with overly conservative NEC calculations.
