I think it might have been a trade-off of using more expensive proportional valves and using a long stick to control the flow for the desired speed. I don't know if a different valve is used on the LX and B and BX, no idea. I would have thought they'd just make a different stick and gimble to operate it based on how long a stick they were going to put on it and where they were mounting it. You know, that parts commonality thing. Seems they realized moving the valve down under the seat would require a locking mechanism for the loader stick on the LX, which is nearly 3 feet long. It just interferes with gimble movement, and mechanically blocks the stick movement. Locking the gimble obviously locks the spools attached to it. Handy when you're not using a loader, but I can see where it would be real inconvenient for it to be something like a thumb latch when you ARE using the loader.
My WC-68 chipper has a latching valve that mechanically latches into place to keep the infeed roller turning forward or reverse. Or, maybe, the latch is pilot operated? The safety bar pivots at the top of the chute, and with the fulcrum nearly 28 inches from the valve, but still has enough mass to vibrate and cause the valve to constantly kick out of forward to the neutral position. Not a bad design, just finicky to adjust. The mechanical travel requirement is reversed with the lever mounted at the valve, which is only about 6 inches long. Travel on the valve spool I'd guess to be no more than about 1/4 - 3/8 inch. If it doesn't stay latched, it's a bit of a pain to constantly have to pull back out on the bar to start it again. There's an adjustment procedure, and I've used it, but it doesn't take much of a turn on the set screw in the valve to get it so that it won't come out of the neutral position at all. The set screw being in the center of the spool makes me think it may be pilot operated, but I haven't dug up an exploded view of the valve yet. More aggravating yet is that the machine must be stopped to adjust it (PTO stopped), with some warnings about adjusting the valve under pressure. You can't tell what the adjustment did until you start it back up. This makes it appear that the detent may have pilot pressure to help operate the spool latch. It's a matter of finding the sweet spot that works, but doesn't over do the intent. Too soft, it pops out of forward. Too hard, can't get it in forward. I'm thinking some nylon crush washers at the top of the safety bar might be in order to add a little friction to the bar instead of trying to do it all with the valve. The ends are held on with nylock nuts, so that tells me they're depending on bolt torque to hold the bar some. I just don't want all that metal to metal pressure with no lubrication points.
Pity we can't get a direct input from the Kubota engineers (or can we?) about the loader valves to ask them why a long lever and super stiffs springs are necessary or was thought to be a good design or why it doesn't give more selectivity. I think that a 'softer' stick would probably be the last thing you want to get smoother operation unless it had a longer travel. The long lever is certainly failing it's intent to soften up operation. Some valves use pilot pressure to help overcome header pressure to operate the valve. MAYBE that's what the adjustment is that's needed? If it's taking too much force to release a pilot valve, when it does release, it's gonna jolt pretty hard. I had to play that game with some hydraulic coil cars in a steel mill. Not nice to jerk 60000 pound coils at 1400 degrees around. They don't bounce good, and usually set stuff on fire if you drop them. I'm pretty sure the stick is flexing as much as it's moving the gimble, and that indicates a binding mechanical device. With that in mind, what's causing it to bind? I'd be willing to bet there's an adjustment procedure for the valves and gimbal linkage to attain best (smoothest?) operation. I just haven't found the shop manuals for the LX yet. Maybe a good careful study of that .......