@jason_b, This procedure will indeed work for an iPhone XS, but I don't believe it will help your situation.
In theory, changing the screen should not affect Face ID, as long as you correctly transfer the front sensor assembly from the original screen to the replacement. Sadly, it is all too easy to damage parts of that earpiece speaker assembly if you don't take the utmost care with it, and if that happens there's nothing else that can be done to get it working again outside of taking it to Apple and having them replace the screen.
So no, this procedure isn't what you want. It only lets you change out the speaker while leaving the rest of the sensor components intact so that Face ID continues to work. It will do nothing if your Face ID is already dead.
The first thing we need to know is, when the original screen was replaced, did whoever did the work transfer the earpiece speaker assembly to the new screen? If not, then your Face ID would stop working. If they did transfer the earpiece speaker assembly, then they did something wrong and may have damaged a component, rendering your Face ID unusable.
In the first case where they simply replaced the screen without transferring the earpiece speaker assembly, AND you still have the original screen, then yes, it may be possible to restore Face ID by finally doing the transfer from the old screen to the one that's on the phone now. That is the ONLY circumstance here where you may be able to restore Face ID.
Here's the guide to replacing those components.
iPhone XS Earpiece Speaker and Front Sensor Assembly Replacement - iFixit Repair Guide
You will need to remove it from the original screen, remove whatever is mounted on the screen you're using now, then put the original parts onto your current screen. If everything goes as planned, you may get your Face ID working again. Note that you may have to do a hard reset or perhaps even a restore to get the components recognized again.