Ev-fw.com can do manual entry if you want and we have see screwups recently but there are at least three Model 3s with 2018.12. One looks like it loaded it twice (same VIN prefix and mileage).With Tesla-Fi, it automatically enters the information for you and so does the Tesla firmware tracker after your initial entry. The latter assumes you set up an account. Anyway, only two showing and one person in a thread said he got this update at the SC today.
As was said, several 3’s have the same version of 2018.12 as the S and X. Verified by TeslaFi.Pretty sure 12.1 is just the Model 3 version of 2018.12, but yeah, my 10.5 (the Model 3 version of 10.4) has the rear seat heat, phone key update, icons update, manual on setting screen... I guess they have all the old changes listed because people don't read what's new with EVERY release. When is the last time you read the release notes on the apps you downloaded onto your phone?
12.1 is a bug fix. I was one of those first 3 Model 3s with 3018.12 and my install failed twice causing me to have to take it to the service center. 12.1 was the fix that corrected the installation problem. The first time it failed, it disabled autopilot. The second time, autopilot worked but the log still showed that the installation failed. While charging afterwards, I was getting a Radick charging for your messages on the app and when I went back to my car, the stereo was blasting at 100% while it was charging. Weird and I hope that that is all now resolvedAll those changes (scroll wheel functions) were in 12. As usual, we don’t know what’s in 12.1.