First and foremost, I don't recommend using marbledcrayfish.com as a source for crays or information, as a lot of their information (even in the quoted paragraph above) is incorrect. Most of it is right, but a lot of it isn't and shouldn't be promoted.
But that aside, Marmorkrebs are very easy to take care of as they can survive a much wider range of tank temperatures and conditions than a lot of other crayfish species. And are easier to house together or with tankmates (select tankmates) because they have a less aggressive personality than the most commonly seen species do.
The only real issue with Marmorkrebs is that they produce a lot of offspring, year round. So, if you don't have a means to dispose of the offspring (i.e. something to feed them to), you'll get overwhelmed in a few months.