I found that I could force encoder steps just by applying slight pressure against the encoder knob without having to go through a detent click. Not at all positions and not all the time, but it just didn't have the precision feel and operation of the optical encoder I have. Like I said it could be made usable but I found them to be rather flimsy in actual operation.
I have one encoder in which one of the transitions occurs more or less at the same position as the detent. My rotary encoder driver software has a 1-state hyteresis to make it insensitive to this. Every encoder I have purchased since has the state transitions away from the detent. The problem encoder has 16 detents/rev, whereas now I go for 8 or 12.