The reactions are definitely positive, and there's another similarity to the man he'll become in the way Thanatos stretches out a little, arching carefully enough not to disrupt anything with a sigh of pleasure and a glint of mischief in his eye. He is entirely aware of how good he looks like this, laid bare on the grass, long hair almost artfully mussed and stretched out underneath the man. He's not quite egging Gustavain on, is more than happy to let him take his time, but there's no hiding how they both want and there's no attempt to.