*** in this case when trying to be scientific in evaluating your original hypothesis of whether POI shifts with different positions. ***
There is evidence in other shooting disciplines that "in some cases", poi can shift with different positions.
However...
New high power shooters generally see up to a 2 moa shift in sight settings between 200 yard standing and 200 yard sitting. I personally experienced this when I shot high power. As I learned more, experienced more, and received professional coaching, this went away to where I had no sight setting shift (just like Morgans grouping pic shows).
There are a large number of variables that caused it. Some translate to prs barricade and some dont visibly seem to.
Correct npa between positions.... the more correct the npa, the less potential wobble.
The tighter the hold and control of the rifle, the less recoil effect. Less recoil effect, more consistent shot placement.
These two will affect prs barricade when the barricade is designed to move or create a higher level of difficulty.
It's up to the shooter to "own" the rifle and control it regardless of the barricade. The better "ownership and control", the less chance of a shift due to operator experience and error.
Off the high power side and on to potential two way ranges.
Training people prone, bipod, bag, and tee shirt, bare head, produces one result.
Adding long sleeves and a hat brim produces a change.
Adding body armor and a helmet produces yet another change.
Training through these stages will eventually provide one rifle setting that produces the same poi.
This is a matter of fitting the rifle to the shooter and at the same time fitting the shooter to the rifle, as conditions require. Once the compromise is found, and it "clicks" in, hits go up....
This translates to the prs barricade as well, but is more difficult to recognize. It goes back to the ownership and control of the rifle, a balance..
In time with practice, and the demonstrated thought ability (visible in his posts), the OP should find this balance, and see the improvements he wants, unless a physical disability such as aging and a rifle too heavy, too "this or that", keep creating the problems that must be overcome.
Best of results to you OP, keep us posted with your practice session results. We all learn something from these topics.