I wouldn't blame HBO there. By written accounts, Maisie Williams was super psyched about that scene with her character and Gendry plus her basic attitude is, "if my acting makes you uncomfortable then too bad; just get over it". The show runners let her go as far as she was comfortable with and didn't pressure her. I could understand her character wanting to experience life to its fullest before a good possibility of her and everyone else she cares about dying very soon. Besides, as consensual scenes go, I thought it was touching (Arya calling the shots with Gendry and doing things on her own terms) considering all the nonconsensual scenes this show has had before (ie. contrasted against Sansa and Ramsay). Her showing off her scars where the Waif stabbed her back in Braavos should put to bed those rumors that she's really the Waif all along. Her being the Waif at this point in time makes no sense to me anyway. Why would the Waif even care to take Arya's face/identity, travel to Westeros, take vengeance for House Stark and Tully, and have all the knowledge that she does about all her past character interactions on top of that?