The adjustment is getting a DE (4-3) or OLB (3-4) into the passing lane for a bubble screen by setting up on the outside of the slot or TE position and rushing upfield then collapsing to the QB. Can't do it with 3 up front and 3 in the second line. It is compounded if the the OLB in a 3-3 can be easily engaged by a tackle or TE impeding the OLB from flowing inside out to the bubble screen receiver. This creates a wide run after catch lane where the DB in cover has to defend both an interior move after catch and out move, instead of being pushed to the sideline. It's a terrible scheme against a bubble screen, especially if the other receivers in a trips set are drawing the other cover defenders away from the area with counter flowing routes.
Finally, bringing up a DB to rush off the edge could work and is contemplated in a 3-3, but it's ineffective if they are blitzing and taking a straight path, which is usually how they are coming when brought. If the DB gets picked by the back or TE, they get easily chipped and neutralized. You need to bring some size with speed. The blitz packages out of the 3-3 are not working because it's the wrong personnel. I don't know why this is so hard to fathom. The empirical information is right in front of everybody. Stubbornness is the down fall the prideful and fear of change the down fall of the risk adverse.