Wholesale checker or Openreach checker?
The Openreach "Where and When" checker that shows exchanges (the one that the superfast north yorkshire website directs you to) can be quite slow to update (although the PDFs at the bottom are updated more frequently). The OR postcode checker only showed my exchange as accepting orders a couple of months after
I had FTTC installed on my line.
The BT Wholesale ADSL availability checker updates quicker, in my experience - a telephone number check on that showed FTTC as available on my line about 10 days after the superfast NY "fibre is here" sticker was put onto the fibre cabinet.
AAISP BT FTTC 80/20 Premium