Hmm, maybe they're not as beneficial to those who fail at midpoint and not off the chest. It's honestly hard for me to believe though that any raw lifter's DB bench could get stronger and their normal bench doesn't get stronger as a direct result. For me personally, if my DB bench is feeling strong then I KNOW my bench is going to be stronger.
How does floor pressing help you? I'd bet that floor pressing, DB floor pressing and 1-2 board pressing would help out a lot. Also, you can do OH pin presses instead of just military press or DB military press, I bet the shorter ROM would translate better if your sticking point is a bit higher than right off the chest.