I have tried this step multiple times and it doesn't work for me. This is a very frustrating issue for sure. I have a 2012 Hyundai Elantra GLS and almost every time I start my car I have to repair the iPhone Xs. I never have this problem with my iPhone 8 that I use for work.
My other car (Ford Expedition with Sync) hasn't had the same frequency of this issue. Over the last month I have had to re pair the iPhone Xs twice.
I have also noticed a couple of other interesting bluetooth issues with the iPhone Xs. I have a wireless speaker and I have had no issues having to re pair the Xs to the speaker, but if I take a call and select to use the iPhone instead of using the speaker, the phone at some point will try and switch to using the bluetooth speaker during the call. I switch back to using the iPhone Xs and it will again switch to the speaker. I have to either turn off the bluetooth speaker or I have to disconnect the speaker in the bluetooth setting of the iPhone.
I have none of these issues on my work iPhone 8 and never had an issue with my iPhone 7 before upgrading to the iPhone Xs.
My wife also got an iPhone Xs at the same time I did and she is also having these same issues on the Elantra and with bluetooth speakers.
I have ensured I have the latest software on my iPhone Xs.