Hi Davison,
I've just realized that your query is about IW33.
Here both the Main Work Center in the HeaderData tab and the Work Center in Location Tab both are taking you to CR03 Tcode.
As I explained in the point 2 of the above reply, this hardly matters.
I consider this is the case of providing 2 Tcodes for the same program. One to suit the PM series of Tcodes and the other to suit the PP series of Tcodes.
See these System Status screens of these 2 Tcodes
Jogeswara Rao K