Although in general I wholeheartedly agree with your transference/resistance theory, I think in this case it was something much simpler. Immediately after putting it down in writing, I shifted from my dry spell to a wet one and returned to a daily practice. I find it interesting that my lack of schedule remained the same, as did my resistance level to whatever else is going on in my life... Essentially nothing changed other than admitting to myself and to you that I had slipped. Amazingly enough, just articulating the fact was enough to invite a tremendous shift. Since one of our intentions with this dialogue was to hold ourselves accountable for and in our respective practices, I think we both deserve a pat on the thoracic spine.
I have much to respond to about the overlap of styles but will save that for another time and instead get into the nitty gritty of your brand new quadratus-lumborum-wrapping party trick. After reading your post, I had to try it for myself and needless to say, you are not alone in your excitement.
My enthusiasm made me google-crazy which is how I came across a fascinating article discussing the psoas and quadratus lumborum working in tandem to stabilize the lumbar spine during seated breath work. This article, which includes stunning illustrations of the muscles moving in the body, is aptly named "Activating Your Accessories." It discusses how the contraction of one evokes the contraction of the other, which sheds new light on your observation that working that deep musculature also initiated uddiyana bandha. Furthermore, wrapping the quadratus helps to draw the floating ribs downward, an action that is both applicable and imperative if you return to the original asana in question - eka pada sirsasana.
So I sat in sukhasana and to be quite honest, couldn't feel my psoas engaging. I pressed down on my knees while trying to lift them up - as the article suggested - and I definitely felt something but it would be a stretch (no pun intended) to say that it was my psoas. Perhaps you'll have more luck. I was, however, able to feel the work in the inversions and forward folds that you mentioned and I am eager to continue applying my new awareness.... Throw in a cup of coffee and it's a seemingly perfect Wednesday afternoon activity. You can thank me later.