Having been in the car business before I can tell you that there is a stigma by buyers for cars with six figures on the odometer. This may stem back from a generation or two before when cars didn't even display six figures on the odo and simply rolled over. Dunno. It's similar to why cars are listed at $49,999 and not $50,000... that one dollar makes all the difference in terms of buyer psychology.
That being said, Tesla wants to disrupt the car industry and is building cars that (according to them) will last forever with minimal upkeep and maintenance during it's prolonged lifespan. You'd think they can disrupt further and help the sale of current new cars by showing that their used cars still have value and still offer fantastic life for many, many years to come by openly accepting them for trade and selling them. Of course their values on both trade/sell would reflect this higher mileage but I still feel that we're at a point in history where people start to realize that EVs built right can last forever and new cars stop taking so much of a depreciation hit since they last forever. People keep talking about how they're computers on wheels so they will depreciate like that but that's just the iPhone crowd that's been buying these new to this point. Once they start becoming affordable on the used market and they start going half a million miles and up consistently we'll see a slow move towards high-mile used EVs by people who are more frugal with the vehicle purchases. Once that happens cars like Teslas will have a reliability opinion that will make current Toyota and Honda brand recognition look like Land Rover in the years to come.
tldr: I don't think Tesla (or any car dealer for that matter) will put enough into a six digit mileage Tesla for trade-in to make it worth your time and you're better off selling it yourself privately. This advice applies to pretty much every car brand though so, from that standpoint at least, they're equal. One place all vehicle manufacturers can find equality... for now.