It’s a sorting of all the mail to the mail carrier level, so yes, they do only need to look at the door number. Similarly the ZIP+4 in the US will give down to

It’s a sorting of all the mail to the mail carrier level, so yes, they do only need to look at the door number. Similarly the ZIP+4 in the US will give down to some fraction of the mail carrier’s route, that they can then sort to a monotonically increasing delivery point number, that is where the carrier actually stops. A full barcode includes the delivery point, but it’s not usually included on the written address.