No, I personally do not see that.
For example, when I map out my cities, I like them plain and not really photo realistic as it is easier to depict individual buildings and features in a city that way (my thoughts). When I zoom down to an alley, I like the more photo realistic, increased detail. Show me the pile of garbage, the broken crates, the homeless hovel against the wall, the drainage gutter etc.
I think the 'style' should, as you state, remain consistent across the whole at the same scale. Again, using Deestan as an example (because I have yet to finish it), if someone was to be mapping for inclusion one of the outlying burroughs, it would jar if it was done with a pallette and style completely different from the rest.