Not that I've read the patent, but that sounds like an SMPS.
SMPS are "constant power" (output) - it was one of their main intentions (aside from removing the low-Hz transformers for efficiency, weight, and international AC inputs).
Battery and related specs have been catering for them for years (since 1990 if not before), hence the typical resistive, constant current, and constant power discharge curves and respective reserve times that are furnished.
It sounds like RIPS is merely a development of SMPS.
[ Not all SMPS are constant power, but since they usually monitor output voltage - as in amps and PC supplies etc - they are constant power output devices. Essentially constant power input too depending on higher current etc losses. ]
So why do many SMPS-containing amplifiers vary output power as if they are resistive?
Me smells some flawed marketing, else VERY strange designs.
(Imagine the M-series etc converters varying output (voltage) with input voltage!)
To quote Stargate's Teal'c "Stange indeed!"