It could have been read as funny, really. Tim was younger, shorter and just generally more compact. Against all odds, he wielded power and he knew it. He knew it now, could feel it in the way that Terry was holding back with him, in the way that he was just kissing when he could have easily knocked Tim back against the pillows.
Tim, well, he liked being in charge. And right now, he'd not try and hide it.
It was Septimus who pushed Terry down against the sheets covering his bed, Tim who nipped at Terry's lower lip as his hands went roaming and did everything but what had been asked of him. Because where was the fun if he got all he wanted straight away? Nothing could ever be unexpected if he did everything he wanted.