According to the following article, the PP wheels are actually significantly lighter (5kg/11lbs) than something - presumably the regular 19"? Or maybe the other 20"? I wish they were more specific...Eh, C&D got 4.1 excluding the rollout, 4.4 with, and carwow got 4.2, both with the Performance Pack, so call my fragile ego skeptical.
Seriously, the PP tires are stickier (more drag) and weigh a little more so the package might be heavier (although the wheels are forged), so a few tenths depending on conditions wouldn't be surprising.
Polestar 2 Performance Pack Detailed