The only reason it is a concern is because this year if you choose to build a 12" tall 6 bar you’re going to want to get that top axle as close to the 12" mark as possible. It is probably viable to do it with or without the top geared and still reach the goal, but it’s something we are considering. We might not even want to build a linkage at all. An arm could be successful.
We have trouble with motors that turn at very slightly different rates, even when driven by the same joystick control. The slight difference in rates causes a bit of torsion, causing asymmetrical lifting and the need for greater clearance on the sides. We had used an rpm counter to try to match our motors (old 3-wire), but we only have 2 HS motors, so only one combination possible. Mechanical coupling helps, but it also adds weight and sometimes creates geometry issues/blocking of scoring objects. Coupling near the pivot minimizes the torque problem, but minimizing problems is not as good as eliminating. I’m surprised that other teams haven’t experienced this issue, especially with 6/8/10 bar lifts. On the other hand, since many of these lifts are above the chassis, having an extra 1/2" of sideways swing due to torsion might not create clearance issues that are important when the lift bars touch the ground. However, as a general principle, asymmetrical lifting isn’t a good thing, and I would imagine that teams would want to eliminate it. We’ve never actually built a 6/8/10 bar lift, so we can only extrapolate what would happen based on the asymmetry problems we’ve encountered with 4-bars.