True, but when LOP the flame propagation slows and running at a bit slower RPM brings the peak power pulse back where it should be. In the max rpm to 85% max rpm range their data doesn't seem to show any worying increase in maximum pressure.
Specifically, in the TNIO-550 they specify economy cruise at 2200 and 15-15.5 GPH which is close to the 25-30 LOP limit they suggest. It also moves my CHT from 300 (15.5 2500) to about 340 (15.5 2200) which is probably reflective of the increase in pressure.