Phillip expected as much, really; give him a challenge, and Gustavain is sure to rise to it. (Pun intended, in this case.)

There is plenty of time for exploration, like as not, because he'll notice fairly quickly that his fingers meet a bit more resistance that he's used to from Phillip. In a way that makes sense, what with this being a brand new form and everything, but on the other hand Phillip could have simply not done that. It certainly opens up more avenues to play with, if that sort of thing is of interest to him. His cock certainly has differences, and even though his pleasure isn't the purpose there's still plenty to be had, Phillip luxuriating under the attention as Gustavain has his fill of exploring.