It may be because the path (which I assume belongs to the neighbour) creates that visual separation and it’s highly unlikely that neighbour would submit an application for a 1m wide two storey extension.
The LPA will always caveat applications that each is determined on its own merits.
Good point, I will stay away from drawing too many comparisons. However it would perhaps be unlikely our next door neighbour or potentially any future next door neighbour would build on the pathway so potentially allowing me to go up to the boundary.