Of course then I realized that despite perfectly symmetrical images, the rotated result with RotateFlip is somehow moved slightly? More probably it's that the DrawImage in conjunction with a matrix transform output is altered from the original a pixel or so in the x/y/w/h. Either way, they give different results and rotating an image through 89.9, 90, and 90.1 degrees causes a noticeable jump in the perceived image location, then a jump back.
Ended up reverting all my FSM changes. This is how you lose half a day