My stupid car engages it automatically. And yes, it's the parking brake. I can hear it engage, the symbol is there, AND in the 'service' menu, you can also see 'Parking brake is on'. Is it a new 2021 thing? I wouldn't doubt Tesla removed the parking pawls from the motors, to save costs. But hopefully we'll know what's behind that soon.
Finally, somebody said the exterior of the 2021 M3 LRs were refreshed, I parked mine next to a 2020, and other than the black trim, the exterior is absolutely identical. And in my case, just for a few hundred VINs, even the headlights are the same. The taillights are kind of crappy indeed. Followed my wife, and they're barely adequate on daylight. Headlights are really good, however, and I like the old ones better, so no issues there.