A splitter node could serve more than 4 or 5 times 12 (the number of ports in a manifold)
You could be right - it would very much depend on the capability of the splitter node held within the pole mounting box.
The original underground splitter nodes are capable of holding 4 individual 32-way splitters, so could serve up to 128 addresses; such a splitter would certainly handle more the 4 or 5 poles.
However, the pole-mounted boxes don't seem to come quite large enough to cope with so many fibres. I've seen descriptions that the boxes come in 12-way and 32-way DP variants, plus splitter variants, but the splitter capability is never explained.
My original opinion was given on the basis that the limit is more likely to be a single 32-way splitter.
Having said that, BT are getting further into considerations of a 2-way split hierarchy, such as this one
. A single pole-mounted box could handle one of the primary splitters, holding 4 8-way splitters. If that were true, then you'd probably see 32 secondary splitters (each 4-way), attached to this - though some of those secondary splitters could be contained within one housing.
With that hierarchy, you'd get one primary splitter for 128 addresses, but many secondary splitters - perhaps one every pole.
The trial of FoD2 with connectorised fibre could change it all around again...