Hi,
In the settings of the plugin, you can configure it to hide the normal address fields or not. If you don't hide them, then when you use the address field and select an address, it will automatically fill in all the fields; and if you don't, you can still manually fill in each field.
Now, we're talking about Google Maps. It should know all the planet's addresses since it is used for GPS navigation all over the world.
It's possible for new constructions, but usually, this affects everything (package delivery, etc), so in such case where the address is not known by Google, people usually add it themselves:
support.google.com/maps/thread/41096368/...in-google-maps?hl=en
Anyway, what you're saying is a good idea of improvement to give the user a way to manually fill in his address when it can't find it with the auto fill field. We'll add that to the plugin. In the mean time, I would recommend displaying the fields in the settings of the plugin if you're worried about this.