Tobias is the type of guy who knows exactly what he wants, no questions asked. He's obviously had a lot of experience and he likes a guy who can keep up with him. Samuel Stone is just that kind of guy -- an eager bottom with a perfect ass and expert dick sucking skills.
The guys actually met a few days before this shoot to see what kind of chemistry they had together, and long story short, they ended up fucking that night. They weren't required to "practice" of course, but what they learned that night about each other's bodies and turn-ons ended up making their shoot ten times hotter.
They started making out in the shower, which seemed to add a sense of urgency -- in no time they were swapping blowjobs, rimming, and then fucking. Then they moved to the bed where Tobias properly reamed Sam and then came all over his abs. With true passion involved, the chemistry between these two boys was completely natural.