Hi
The checker doesn't appear to know if an existing service is at the property or not, just seems to report on the basis there isn't.
Also you can understand why they wouldn't want to install additional fibres to a single property as they don't tend to install with much spare capacity, i.e there may be an 8 way port at the DP that serves 8 properties, okay not all will take up FTTP at this time so there may be spare ports so someone could take 2 or 3 even of those to the same property, but later at copper switch off when those properties have to join the fibre network they find there are no connections available at the DP.
The easier technological solution is of course multi port ONTs, but still this creates a potential problem if Openreach only wish to share a single fibre between a maximum number of premises.
The other reason not to supply it; why would a non commercial property require 2 or more fibre connections? If someone needs that much capacity they should pay for a leased line or go with another fibre provider (other than Openreach) in the case of over build as clearly it isn't typical domestic use.
Regards
Phil