The way Openreach surveys for FTTP are undertaken , and the way the work done on retro build FTTP doesn’t really align with the way the OP states
….if an area is surveyed for FTTP , the surveyor doesn’t ‘knock on doors’ to have discussion with the householders about potential uptake etc , at this point they have no idea if the survey (once returned to those that control the budget for the build phase ) will actually be an area upgraded or surveyed but remain outside the current build plan , if a surveyor was asked during the survey ‘what are you doing mate ? ‘ , no doubt they will engage with that person , but apart from general info , they can’t give any particular helpful information as far as dates etc , it may be years before the build is started after the survey is done .
Once the build phase is started it’s dynamic , and under control of the local build management , should an area (within the general area to be served ) hit unforeseen snags , ( a problem occurs that will be disproportionately expensive to resolve ) , that part of the scheme can be deferred , so basically you can get a small enclave that’s omitted from the rest of the build taking place around it , because the costs for those few properties are outside the budget allowed per dwelling.
Any scheme that is started is not influenced by potential take up of the service, you can’t order FTTP until the network is built , so how can any area have ‘not enough takers’ beforehand, when the build is taking place Openreach have no real idea how many takers there eventually will be .
FTTP is built without any orders existing for it , in simple terms it’s impossible for anyone to order FTTP from an ISP until availability is showing and that’s only after the build is done .
There must be more of a story behind this , perhaps the OP will give more detail.
