Those rules remain on the books, though there's more reluctance to actually impose them these days because of the inherent difficulties proving frivolity has in a court of law (that is not the FIA one). Unless you behave like Eddie Irvine did in his appeal case of Brazil 1994, you won't get the penalty increase.
However, it does cost €15000 to go to appeal, so if you aren't going to win the case, there's not much point paying. Especially if you know an appellant is going to pay that €15000 for you, and that Racing Point is doing so (albeit for the opposite reason). Since, unlike a court of law, the FIA courts allow penalties to be increased as well as decreased, and it is possible to submit evidence without being an appellant, Renault may have decided it's simply cheaper to participate as an observer.