Proper fundamentals mitigates bipod hop.
This isnt theory, you reduce a significant amount of stability having the bipods closer to the axis. Youre creating a tripod with the bipods and rear support (3 points of contact that will always create a plane). With respect to the height of the tripod, the closer the 3 points of contact are together, the greater the instability. Now, in regards to the rifles stability, we are talking about stability of the x-axis (fore and aft). Since the the rear of the rifle is the only part of the rifle thats going to be moving vertically from breathing and any adjustments to the rear support, this makes the bipod the center axis , where the rifle is going to rotate on the x-axis around that fixed point.
I can keep giving you examples about how widening the foot print will increase stability, however, try this in a real world situation. Find a regular forend, mount the bipods as far out as you can, using the monopod, rotate the thumb wheel 360*, while looking through the scope preferably while on target, and note much vertical deviation there is using the reticle. Now do the same thing but with the bipod mounted as far back as you can. Ive shot this way, its very possible but small adjustments to my rear bag were magnified compared to the normal bipod mounting distance. I had to be even more precise and attentive to my adjustments.
Why would longer barrels be frowned upon? If you had bipods mounted at the magazine on a traditional rifle, sure, the heavier and longer barrels might make the rifle tip forward, however the only people using those lengths and contours (1.350 straight 30"-32") are ELR shooters, and note the bipod location.