For this container, that wont happen with that variable in mind. You can create an account by using the variable for allowing sing ups.
For the lsio container i brought up, it means that it wont create the user automatically on startup, you can still create it with the containers shell with the same commands you would use to create user 3 currently.
You do inn fact bring up an interesting point, and see where the template maintainer may be able to mess it up.
This whole discussion will probably fit another thread (please point me to it), but it would also be nice to be able to have variables connected to the branch tag. For this container its not needed, as its sql based counterpart is another image, and introduces some variables.