Doug, can you explain what you mean by "common folding knives with a bias toward closure"? I've never heard that terminology before.
EMPnotImplyNuclear got it right. Virtually all folding knives except automatic (switchblade) knives have some mechanical means of keeping the blade closed while in your pocket, using a detent, spring, friction, etc., to prevent injuries. They are "biased" to stay closed and are designed to be opened only by moving the blade to overcome that tendency to stay closed. Because bias towards closure varies widely by design, manufacturing tolerances, wear, etc., some open more easily than others.
True Gravity knives have no bias towards closure or opening. They have a lock to keep them closed, but once the lock is released nothing happens unless you point them towards the ground or apply centrifugal force. Because there is no bias they open readily the same way for every person every time.
Automatic (switchblade) knives are biased to open, the blade wants to open and only stays closed because of a latch. Press the button or otherwise release that latch and the blade springs open.