The rationalist movement, if it is anything, is a movement defined by the desire of its members to perceive the world accurately and without bias. In that sense, using a variety of different tools from different academic and intellectual disciplines (philosophy, economics, mathematics, etc) should be expected. I don't think any of the major rationalist figures (Yudkowsky, Julia Galef, Zvi Mowshowitz) would claim any credit for developing these ideas; they would simply say they've used and helped popularize a suite of tools for making good decisions.