Then you heard wrong IMO..
From folks who worked closely with Bruce, including Dan Inosanto and others.. They all confirmed that although he played with lots of stuff,
when things got serious he would almost always enter (into close range) and use close range tactics.. (WCK though call it whatever you like.)
Makes perfect sense to me because this is not only the thread that ran though everything he did but it is what he did the longest, it was still his specialty. Now to be clear this doesn't mean he didn't see its (WCK/ChiSao) limitations but it also doesn't mean he tossed it, since he didn't.
This is also supported in part by
VIDEO from the Long Beach Nationals where he demonstrated Both JKD AND ChiSao.
What this means is that ChiSao made it past his JunFan stage into his JKD (last) stage.. If that doesn't clear this up for you then nothing will.
http://www.youtube.com/watch?v=Tl2vxgCuPXY
Moreover, "trapping" as you call it is one of the ranges included in JKD and accounts for much of the training--
including the training he gave to Lewis and Norris. Odd for something you claim he didn't find useful as time went on. The FMA influence in JKD later came from Dan, not Bruce. (see how we often go back to our roots..)
If you have
any documentation or other evidence that says otherwise feel free to share.