I got the tow hitch installed a month ago at Tesla (on my 2021 Y). The new "trailer" setting appeared on my menu (2022.12.3.6 here).
Could be they forgot to install the software, but I also heard the new lithium battery isnt 100% compatible with the tow hitch accessory port. Something to do with voltages I think (15V vs. 12V??), apparently something needs to be installed downstream, like an adapter or something, to make it work right. No idea on the status of that. I did make a note of it in a thread I keep regarding MY changes over time. Most updates in that thread are from hearing from various owners, but its the best info I can get.
That said, you should still be able to manually do it. I'd think. Hopefully they just need to change a flag in your SW configuration.