When were these houses built approximately ? , from early 1990 onwards a fully ducted network was used by Openreach (BT) , the only exception really was sites that had a sweetheart deal with Virgin and effectively locked out BT/Openreach , so somewhere having some grey Openreach and some brown Virgin but some with only Virgin is unusual ( FYI although the cable industry did use brown covers the duct is normally green )
It may be a regional thing , I’ve a vague recollection that in some areas BT may have used brown covers instead of the more usual grey , but in your case the brown covers seem to indicate Virgin , and it would be odd for BT to use some brown and some grey in the same location.
As the Openreach survey note states duct exists, raising an order won’t be affected , you will be able to order FTTP , but as stated , the potential problem is if the installer turns up to discover only Virgin ducts exist and not an Openreach one, that will cause a delay while a way to get a cable from the footpath to the house wall is provided
