They didn’t really “leave” Reflections, because in that case they “left” all the time. They probably “left” because the company Reflections has to stay alive and continue making money, the brothers themselves however weren’t interested in working on the projects that kept Reflections alive.
If I recall correctly, Martin had partially “left” for Driver 3 too, and in return, Martin had completely “left” for DPL. Then, they both “left” before DSF and eventually they came back because they were asked.
And I bet that for the next Driver they will “come back” too and then “leave” again