You mean roll back to 20 tier system?
Although your numbers sound logic there are certain circumstances why this doesn’t reflect the reality. A short example:
Try the Italian P-47 D-30 in Air RB. You will get currently 85-95% full uptiers to 6.0 - having the honor to play with 4 Ju 288s and another fighter vs 6 US/UK fighters, usually outperforming you by massive margin. The full uptier ratio decreased during the spam of the Italian Battle Pass 109 F-4 to around 75%. I played more than 300 battles there. Last week 1 battle there, ofc a full uptier.
Playing with the almost identical P-47 D-28 (same FM, just no air brake) also at 5.0 in Air RB i haven’t had a full uptier in my first 25 matches, so no fights vs Ju 288s. Battle no 26 & 27 brought 2 full uptiers to 6.0 - as fun fact those were mixed battles so both teams had 288s with them…
With this small example you might see why your are right in theory, but reality might be different.
A last word regarding correlations between player skill and full uptier ratios:
As gaijin has not published all factors which are considered by the MM nobody can claim that this is not true. Even without wearing a tin foil hat: If you play the game long enough at certain BRs you see patterns within the MM supporting this theory - somehow current performance, relative WRs or overall stats are considered, at certain points (after long win strikes) your team mates become less experienced (to be very polite) and you play a hell of full uptiers.
Where did you find that chart?
It’s normally on the BR change posts but I also made my own copy.