Reflashing 2019 AT with 2020 code?

Yes. If you pay for a subscription to TiS, load up TechStream, buy a cable like Tactrix, and do a Health Check, it will tell you if there is an available update. The system is foolproof, so you cannot install incompatible updates.

That said, you can brick an ECU with TS.

Like the ECU TSBs in the past, it is easier and cheaper to just monitor TW for actual info.

 

That's why I'd be interested to know if the latest image can be reflashed. Changes may seem relatively minor to any maps and/ or tables but the code itself (algorithms) could be significantly different.

From the video it sounds as though the TCM update was specific to the '20 but I guess it's possible the update was implemented in production towards the end of the '19 run.

I've taken a '19 for a short test drive but haven't yet had a chance to drive a '20. Not sure what you could learn without driving each over an extended period (at least several hundred miles) under varying loads and conditions.