If the input force is very high (e.g. equal to the peak detent force), the detent releases almost immediately as the force applied is the same as the peak force. At this point, the normal force on the cone clutch drops considerably, and it does not slow the relative rotation enough to allow locking.
To alleviate this you should ramp up the force over time. This gives the cone clutch enough time with force to slow the rotation sufficiently. You could construct their own synchronizer out of similar blocks as the built-in blocks to match the type of synchronizer that exists in their system.
Another option would be to use feedback from the system to control the force applied. This is precisely why position outputs are built for this block. The information from those outputs plus a rotational motion sensor could be used for a controller synchronization.