I’ve not tested this, but I doubt HPA as a propellent, compared to green gas or AEG has an impact on accuracy once any other factors such as B.B. bore consistency, weight, barrel bore, barrel length etc are equal
Ultimately the path of the ball is defined by its route down the barrel. There is some science in what happens when the ball comes out of the tip of the barrel - hence lots of variation in barrel tip porting designs in Paintball which may or may not affect the ‘shock’ of hitting the atmosphere by easing the pressure in the last inches and the noise on exit on discharged air direction
Different configurations will certainly affect consistency, which isn’t directly accuracy but inconsistency will lose any ability to predict where the ball will go
The idea of different gasses an accuracy is somewhat true, but not how you may think.
Green gas freezes up in cold weather and becomes less powerful, near the end of mags shots can be less powerful if spammed and the gas cooled.
Co2 has a smilar problem but only "just" as it survives cold far better.
Air form HPA is not affected by the last phenomenons.
Now accuracy: it's not "accuracy" but shot power (fps) consistency.
If ever shot fired at 300fps exactly, regardless of power source, and the barrel was totally smooth and clean of any debris, then all your shots should in theory travel in a similar path (even if it is not accurate, it will always be "off" the same way consistently), allowing you to adjust your aim.
HPA is the most consistent of all power sources with air leaks really only possibly at the hop unit.
C02 is also good for this.
Green gas is very inconsistent in cold weather but on par with Co2 in summer/warm.
AEG can be very consistent when you polish, smooth and seal everything for no air leaks.
TL;DR - doesn't make accuracy difference, makes shot power more consistent, means inaccuracy is consistent and therefor user can make the weapon accurate by hand.
