Can you describe at least the outer form if not the inner?
Interesting that they are recent. Did he say where they came from? That might be of interest to me..
Dan- I wish I could tell you more. I started noticing more of these "exercises" maybe starting 3-4 years ago. Sensei did not voice to me from where he derived his exercises or new[er] explanations; I did not presume to ask though. My suspician is that timing is awfully close to some serious overlap with Ushiro Sensei visiting Colorado, getting involved in summer camp, and spending some time with Ikeda sensei. I got suspicous and bought some Ushiro sensei DVDs from Sensei when he was in SC last year. I am looking through them now for an origin and to see how the exercises relate...
As for many of the exercises... I have seen a number of old-skool stuff, (torifune, sayo undo, hasso/happo undo, zenpo undo) coming back in style. These are centering exercises exploring the directions of extension while maintaining balance and posture. Now, these are not the sloppy, "throws your hands out and back" stuff, they really remind me of stance-building kata and proper breathing.
Another series of exercises I have seen are a little more touchy-feely. Your partner assumes a strong/comfortable stance and you apply an external pressure to solicit and shift in balance. This is where Ikeda sensei talks about the "aiki" connection - at the point preceding interaction. Some amount of this exercise is focusing on where you want your partner to feel pressure from your hand - his back foot, his front toe, his inside back knee, etc. Ideally, you're reducing the amount of pressure applied while achieving the same balance shift.
Truth be told, I do not know if these exercises and demos would qualify as internal strength or not. To me, it seems clear we are focusing on centering ourselves and becoming sensitive to how we connect with our partner. 20 years ago, Kuriowa sensei would probably just call it kihon...
Also, it may be that Sensei has been doing the same thing all along and he is just better explaning it now; part of that improvement may be his [better] selection of exercises and explanantions...