Monroe dampers are deigned to become progressively stiffer as they compress, making them quite sporty on a lowered car. I've used them with 25mm springs without problem. If you go stupidly low, you may get problems with not enough travel, as well as sprigs being loose once the car is jacked up, which can give problems with TÜV or MOT.

So they are half way correct - for huge drops you need special dampers, but for 25mm or so they are fine. Huge drops are obviously no good for handling, so it doesnt really matter what dampers you use, so long as they have enough travel and pass the safety test.