The 2020 Model 3 Performance is the only model year 3P that has three separate ratings on the fueleconomy.gov website. One for 20 inch, 18 inch, and 19 inch wheels. All the other model years of the 3P have a single EPA rating.
Does anyone know why Tesla did this for one model year only? Does that mean that the range on the other 3Ps is not impacted by wheel size? I highly doubt that.
The wheel and tire difference is the entire
difference in efficiency between M3P with Performance Upgrade Package (PUP) and M3LR AWD, or nearly all of it. In theory the PUP spoiler or brakes could affect efficiency too, but I am sure Tesla optimized those well and they don't add any significant drag. (Aftermarket brakes and spoilers could be a very different story of course.)
For 2021 Tesla made the PUP standard on all M3P. No reason to perform EPA testing for M3P on 18" or 19" wheels when no longer selling such a config.
I don't know why Tesla only started filing separate EPA ratings for optional Model 3 wheels in 2020. It's worth nothing this applied to the whole Model 3 lineup, not just the Performance. There's no optional wheel EPA ratings for any Model 3 version prior to 2020.
My guess is either the EPA has been more strictly enforcing a preexisting rule which requires separate ratings for options that meet some expected threshold of efficiency impact, or
car makers are simply realizing that for EVs the impact is more relevant, consumers would feel misled if they paid for a less efficient wheel without being told the impact.
It looks like Tesla started filing separate ratings for optional Model S wheels earlier, but didn't carry that practice over to the Model 3 until 2020.