VNY to SILEX just like LAX to SILEX are feeder routes to the IAF. FIM and VTU can be used as IAF's for the approach. Size/color of line from FIM to TOAKS varies in order to make the radial (136 off of FIM) also useable to ID TOAKS. Radials from LAX and VNY are also/can also be used to ID intersections on the approach.

Ex. You are using VTU as your IAF, ATC says report TOAKS, how can you ID where TOAKS is (amongst other ways) Intersection of the FIM R-136 and the localizer off of I-BUR. TOAKS cannot be ID'd off the intersection of the VTU R-054.

Thats my take on it at least, hope that makes sense. If anyone else has an opinion on it, please advise.