Openreach have a big problem with data integrity of addresses, as they end up dependent on the ISPs to get addresses right. That isn't a trustworthy source.
The scheme to try to keep on top of this is through the gold, silver & bronze keys.
For a "gold" address: BT have provided service to this address, so this address is taken as a correct, valid one (even if it isn't always).
Addresses that have not had a BT service are "unknown", and fall into 2 camps: a "silver" one, where the address comes from the Post Office Address File (PAF), and a "bronze" one where the address is not known at all.
Both of the last types need confirmation after the order is placed, and this is done by a survey of the premises and a manual check of the address entered.
When I moved into my current property, and ordered a phone/broadband service, the "silver key address" was surveyed within 48 hours, and the checker was updated to give both broadband and FTTC speed estimates. Well before the installation work was due to complete (and, in fact, well before we moved in).
That was the good news.
Unfortunately, the surveyor got his data wrong, and typed in the wrong cabinet number. It meant that FTTC orders kept failing, and took around 3 months to fix.