Do you know if it was made in Fremont or Texas? I wonder if there are any differences in VOCs between Tesla made in different states. CA is very strict about VOCs (I know from different construction/paint materials that are not allowed to be shipped to CA or are a different low-VOC version for CA only, so CA is pretty much the strictest state). There will always be some "new car smell," but I imagine a CA made one wouldn't have as much VOCs as others states.
I personally didn't notice a new car smell when I picked up my Model 3, but it was Fremont made. I also had the fortune to still have a 2nd car and was waiting for Tesla to have time to address a few delivery issues (so I had it in the garage unused to keep it under the 100 mile mark, to avoid any disputes on whether the car came), so by the time I was using the car regularly, I imagine most of the offgassing is gone.
I wouldn't however be too sure if your air quality monitor is really measuring offgassing from the interior or simply from the VOCs from the environment that would get blown about at a higher rate when you have the climate control on. A more controlled experiment would be to blow a fan with windows open on the Tesla (if monitor is outside and can't be moved in) or windows closed (if monitor can be put inside car), then have an older car and do the same (both cars having been driven a bit in the same environment or sitting for the same amount of time to try to eliminate variables).