Joe,
IMHO, just because the lock is a "Lock back",
doesnt mean a spine whack or other use will disengage it.
Any lockback, especially one that's used or been carried can fail. A good example is if any crud gets in the blade notch.
An even better example, is under stress, while using or "gorilla gripping" it is fairly easy to inadverdently disengage most any lockback with direct palm pressure on the lock itself.
Most of the front-locks out there will easily disengage with (hard) hand pressure. All else being equal, Tail or back locks seem to be strongest, although Cold Steel's Midlock is awesome. (just dont do any lateral
strength tests on zytel handled knives)
I'm with you regarding many of the frailties of a liner lock. However, the lock-back is not the answer. They have their own list of
poor qualities that most of us have "forgotten".
The Pack River folders are beautiful, though and I want one in CPM440v. Mullin has been using that stuff for a long time and he probably has a pretty good handle on its intricacies. Flat ground too!
Remember, YMMV