As you may already know, Pierce sensei started Aikido in 1960 and until in 1974 he founded the N.J. Ki Society, he had trained in Aikikai for 14 years and got all his ranks from 6th kyu to 3rd dan. When I told him that I read in this forum that a lot of Aikidokas are seeking to "bring Aiki back to Aikido" by going to some other martial arts to study the Internal Power/Ki, he said the Internal Power/Ki training had always been a critical part of Aikido curricula during his time in Aikikai, it's sad to see that critical part had been banned or lost in today's mainstream Aikido trainings.
I've never met him, so I can't say that what he's doing is the same as what the "internal power" advocates are doing. Of course, he can't say that either, unless he's met them, and the above seems to imply that he hasn't.
The "we already do it" answer seems pretty common - in people who haven't actually met up with those guys yet. I will say that I've trained with a lot of Ki Society people - all the way up to the top, and it didn't seem to me like the same thing at all, although there are, of course, overlaps and similarities.