There's another element too, in relation to pressure - a big one.
The tyre (any tyre) is a huge spring, and substantially undamped in its action. Try bouncing a car spare wheel with low psi inside, then vs setting it at 25psi. There's massive difference between the two in returned kinetic.
This, particularly rear, interacts with aero load+GF+chassis spring/damper control as the tyre has it's own frequency that may conflict or complement the chassis dynamic and track surface height variable in use.
Changing the pressure WILL change the frequency of response. This may be helpful or destructive for different chassis & GF concept running in each team's car.
When we hear "bouncing" that characteristic "chuff, chuff, chuff" is very similar in each car, indicating that it's derived from the dynamic excitement of the tyre (reasonable projection as that being common denominator) in producing sympathetic response within the tyre structure. Observe the tyre "squelch" in 2022 at first test phase of that season to give visual representation.
If McL have this sorted in control of their own bouncing (it seems that way) they can logically run the car lower at rear to leverage better GF load, that without excitement of the tyre into uncontrolled oscillation.
Within engineering solution to vibration/frequency, is the action of moving one component's frequency out of range of the latent frequency occupied by other hardware. This can prevent it being a problem that destroys an equilibrium.
Equally, if another team has not got on top of this aspect (some still go into this phase) but that shift upward in pressure results in untangling that frequency conflict, then that could also allow the "poorly" performing chassis to advance into the same performance arena as McL 39.
It's a compounding gain too, reduced sensitivity and onset of bouncing, then allows that "corrected" chassis to be run lower and still not breach critical frequency, moving it further forwards in performance terms .... all the while the pressure increase cause no tangible gain for the 39 as it was already effective in its management of this aspect.
Then we can see these relationships pull and push on different track types, while team personnel expressed mystery as to what happened.
