DB's website does say the following though, on this page:
https://www.deutschebahn.com/de/presse/suche_Medienpakete/Neues-Design :
Which (roughly!) translates to:
"For the seats alone, about 200 material samples from seven manufacturers were tested. In an eleven-month development process, the materials were thoroughly put through their paces. In particular, the seat upholstery is subjected to a variety of trials and must fulfill high standards in abrasion, resistance to light, cleaning results and fire resistance. Additionally, numerous tests were undertaken by an external testing institution. The materials were soiled with coffee, chocolate, hand cream or felt pen, in order to test if, and how well, they allowed the stains to be removed. The seats being trialled were abused around the clock by special apparatus, to simulate many years of use by tens of thousands of passengers".
So it looks like they've put some effort into choosing which flat cloth they use, and hopefully it won't stain as awfully as Northern's...