After testing, it appears that yes it is as simple as it seems.
The local databases are upgraded when user first reconnects.

One advice : I prefer to use the full command line with all the switches. In case the parameters were not retrieved automatically.
So a good practice is to write down the command you used for the install, so that you can re-use it for upgrading !
Otherwise, you come back two years later, and don't remember at all your custom command !