PANS is designed so that the combination of PANS and a DWM1001 has FCC modular approval. This means you can use that combination in a commercial product without having to carry out extensive (and expensive) radio transmitter testing. The instant you change anything about the transmitter (preamble length, data length, transmit power, channel, antenna etc.) that FCC approval is invalided.
When running PANS the transmitter power, together with a lot of other transmitter parameters, are locked to the values used when that FCC approval was granted. You can’t get modular approval on something that makes it trivial to violate the limits.
You can always write your own firmware with different settings. But then you need to get your own FCC (or equivalent for wherever you are) approvals if you want to sell it…