They are alluding to the fact that Dark’han is predatory in a sexual way. Him guarding her body implies sexual deviancy.
Even though it’s not explicitly stated. He defiled her corpse.
Blizzard leaves a lot of these thing implied, but it’s heavily implied that Sylvanas’s feminine intution about him was right. He’s a predatory creep and Arthas gave him her body to be alone with.
Arthas created this “sleeping beauty” narrative around her too. In the original fairytale Sleeping Beauty was defiled by The Prince as she slept. This is no allegorical accident.