Because I had some spare time and an unused WCP to play with, I just tried to make an ex-Europe Latitude booking for two, using my WCP.

The process seemed to go smoothly, I was able to select the WCP as a valid pass - and as expected, that limited me to purchasing only economy seats (meaning that it really was recognizing the WCP option correctly).

I selected two flights with the latitude fare, and everything looked good. Until I got to the travel summary page ... and that is when the system said that my WCP was no longer applicable.

So it certainly appears that something about the WCP process is currently broken. Hard to know if it's a policy change, or just a broken IT system ...