That figure should be taken with pinch of salt, of course.
It is industry practice to record 'properties passed' when rolling out cables. No-one counts actual connections because those will only be made as/when/if the property owners choose to take up the service and may never reach 100%.
However what they shouldn't do is regard a property as passed just because it is in relatively close proximity to the cable. Most of the time it doesn't matter but if a property at the end of a street is accessed via a bridge over a canal it shouldn't be considered 'passed' unless the fibre has already been taken over the bridge or if the bridge is known to have viable ducting or suitable poles to carry the fibre.
So if by 'pinch of salt' you imply that OR is lying, then no. OTOH if you mean that engineering always has a little wiggle room then maybe. Call it 12.5 million +/- 500 ;)