Hi Bob -- Sort of, but I'd put it a little differently. I would say that the amplifier stages of the power amplifier are isolated from noise and other garbage that may be present on the ac line by:
1) The rectification (ac to dc conversion) process, and subsequent filtering, that occurs in its own power supply.
2) The rectification (ac to dc conversion) process, and subsequent filtering, that occurs in the power supply of the power regenerator.
3) The fact that the audio amplifier's power supply is essentially not in the signal path.
4) The fact that the power regenerator essentially breaks the path between ac from the wall and the ac input to the power amplifier, since the ac provided to the amplifier is derived from the regenerator's internal oscillator, and is amplified by circuits that are isolated from the wall ac by the regenerator's power supply.
Without the regenerator, you just have nos. 1 and 3, but not 2 and 4.
"Filtering" of ac to me means something conceptually similar to putting an inductor in series with the ac line, and a capacitor across the ac line. Both of which tend to block high frequency noise components. And that is conceptually what a line conditioner does, while a regenerator will eliminate anything and everything other than 60Hz (not just high frequency noise components), including for instance 120Hz and 180Hz and other harmonic distortion which may be present on the power line.
BTW, I should add to my previous comment about the cost, size, and weight disadvantages that regenerators may have, the fact that since they are high powered active components they may themselves consume significant power, increase electric bills, add heat into the room, and possibly add some degree of noise as well, if they are fan-cooled. So there are lots of tradeoffs to consider.