Well, you have an obvious choice about what to do in this scene. You could have gone the other route and not let it happen. In fact, in that case, Rin would have been grateful to you for stopping her. :)
The main idea of this update was to show how Selene's powers affect Rin. How it pushes her to do more and more reckless things. We don't plan on making Rin's root and our game all about sharing and swinging. We want to show that Rin's mental boundaries are getting thinner, and it's in the hands of the MC how low she'll stoop. In that sense, that glory hole scene served as a tool to accomplish that goal, not as the start of a new sharing or swinger branch.
That said, maybe we'll add 1-2 more sharing/swinger scenes, provided MC made the right choices in the glory hole scene, as a logical progression of that route in Rin's mind (The player will always have the option of not allowing it). If MC stopped her, she simply wouldn't do it. We would also like to point out that we've stated many times that our game does not and will not have NTR content.