Choran, I read your question in post #5 and repeated in post #8.
Thanks to Jason for starting this informative thread with his composite photos. I for one have found it to be very instructive particularly in the light of our many PMs pertaining to the use of secondary mirror masks.
I cut the LH image out of the composite photo, enlarged it (zoomed-in so to say) and then brightened it up a bit. When doing so I was also able to see the beginning of the coma effects around the perimeter on right hand side of the image.
To take a stab at answering your question Choran, and quite possibly subjecting myself to the ridicule of my peers on this forum, I'm going to suggest the following as I think it through for myself. Please remember that I am not speaking for Jason here. This is my contention only and I really do understand that the purpose of the intentional mis-collimation in the OP was to instruct, not to deceive.
I suspect that we are seeing the shadow of the secondary mirror almost perfectly centred, despite the intentional mis-collimation, due to the actual mis-collimation itself. You will recall that Jason has intentionally mis-collimated the primary by turning just one of the screws.
I am of the opinion that if we were able to see the same defocused image before the intentional mis-collimation, we'd probably see an offset secondary shadow in the image. In other words, when the single screw intentional mis-collimation was performed, it tilted the mirror in one direction only and that shifted the shadow inwards from an offset position to a more centralized position.
Of course, this does not mean that the single screw mis-colimation could not also have caused the offset shadow to shift outwards the other way, thereby increasing its displacement from the centre.
We know from his other posts that Jason is using a secondary mirror in this 10" scope that is configured in accordance with the Modern Method. In this Modern Method the secondary is configured without a radial offset. Even so, in a perfectly collimated defocused scope at a much lower power say 60x, i.e. 6x per inch of the 10" mirror, we would still be able to see an apparent radial offset of the secondary which is caused by the tilt of the primary's optical axis away from the centre of the OTA and towards the focuser. The single screw intentional mis-collimation of such a scope would probably cause the optical axis, and therefore the defocused offset secondary shadow, to shift inwards to a more centralized position.
Perhaps, this low powered view of the defocused secondary shadow is also visible at the higher 200x power that Jason used in these photos. For me, 200x is about the highest useful power that I can get under my sky conditions. For others, 200x is only just the beginning as they target 400x - 500x with ease. For these folk, a low powered star test would be at about 200x, a high powered star test would be at much, much higher powers. It's all relative is it not.
Now, let the flaming begin! And if not, let our learning continue. The class awaits.