"Non-compliant" does not mean realistic ("alive"). Chi sao is non-compliant drill (your partner doesn't just let you do whatever you want). However, it is completely unrealistic (people don't behave as they do in fighting). Doing non-compliant but unrealistic drills won't produce realistic skills (skills that work in a realistic setting). The only way to develop realistic skills is by training realistically.
The truth is lots of things we can't make work, no matter how long, hard, etc, we train them. Some of these things are individual and some are universal.
On the matter of "trapping" -- many good fighters "trap". It takes place all the time. Thornton, if you roll with him, will trap your arm before he goes for an armbar. Wreslters do it. It happens in the clinch all the time. What I think Thornton is talking about is "WCK trapping" as it is typically demonstrated (in chi sao, for example). This is because many people mistake the drill for the application, and think actual application will look and work like the drill. It won't. This is why when WCK people fight, they have little skill (they are trying to use their WCK tools as they do in the drills when fighting). But many WCK people believe that drill=application (how you do it in the drill will be how it works). And Thornton, seeing the drill realizes from his experience, that those things will never work as they are being practiced.
Terence