If you know anything about outside plant operations, you know that lots of maps--especially “as built” maps--are not fully and accurately updated. They should be, but they perhaps are not. That can result in discrepancies between the way a service provider believes specific network locations are configured, and the way they actually exist.
That is not to say malfeasance is never possible, but it is much more likely that maps are incorrect simply because, over time, not all the changes are reflected in official maps. To use a simple mobile analogy, coverage maps indicating data speeds will show one set of numbers in the winter, and a different set in the summer, where there are lots of deciduous trees.
It also is possible fixed network data speeds will show one set of numbers at the hottest point of the summer and the coldest part of winter, or even different performance based on thermal effects across a day or a week.
Temperature affects both processor and cable performance, for example.
Measurements for parts of the network that are newer might diverge from parts of the network that are older, even in the same neighborhoods.
The point is that there are lots of reasons why end user data speeds are not as the maps suggest they should be operating.