That doesn't imply any number fiddling. It proves that your parent's house has indeed been passed so should be counted in the statistics. Typically that implies service availability to those properties but there are sometimes delays in the fibre actually going live (as in the other poster I replied to who had the fibre but couldn't get a connection).
However what you describe sounds mad. Utterly bonkers. Connecting a property to the fibre is only done to provide an active service. What you describe is akin to a restaurant letting you sit down, order a meal then tell you that the kitchen is closed. If this is the case then someone has cocked up big style. I'd be tempted to get your parents to switch to a different ISP and see what happens.
As for the landline removal though that is a separate thing. There's no requirement to remove them so if it's not worth the effort they will leave them in situ.