Is it allowed to lay KG pipes in gravel?

Split / gravel serves as a drainage layer. Fleece around it (not around the pipe) to keep dirt particles out (clogging..) The pipe is not damaged as a result

So far so clear. But can't the gravel damage the drainage pipe, while a KG pipe can?

Apparently not clear: Gravel as the bedding of the pipe, i.e., underneath it, only made sense for drainage if it was meant to discharge rising water - i.e., pressing water - which seeps but flows downward. And yes, the hard breaks the brittle. Sand is used precisely because it is finer-grained than the soil - the gravel is coarser-grained, thus exerting more force with its edges.

Additionally, a hole or crack in a drainage pipe is simply less dramatic than in a sewage pipe. It is obvious.

Well, there are also species that lay thick nyy-j (underground cable) for an industrial hall in basalt grit 2/5. It will surely hold until the guy leaves the yard. He was still allowed to dig it up again and sand it properly.

Gravel / crushed stone serves as a drainage layer. The fleece is placed around it (not around the pipe) to retain dirt particles (to prevent clogging). The pipe itself is not damaged by this.

Our construction contractor wrapped the fleece directly around the drainage pipe. At other construction sites, I have seen that gravel (8/11) was laid, then the drainage pipe + a bit more gravel, and then the fleece was placed on top. (Very different approaches depending on the company). To wrap the fleece around the entire drainage layer, you would need a roll that is wider than 1m, otherwise you would have to wrap the drainage layer meter by meter. (with a bit of overlap)

Both are possible, depending on which load case you want to drain, sometimes one makes more sense, sometimes the other. There are also DrainPipe with coconut mat wrapping, which is supposed to fulfill the filter effect of the fleece and of course simplifies the installation.