: Curious. Why does such a thing exist? What's next? hydraulic paddle
: length and feathering adjustment?

The main benefit (for us) is the possibility of routing the cables anywhere you want - it may help moving the cables out of the way of hatch gear packing. Another benefit (that I'm not sure is used here) is differential control/actuator movement.

The downside though, is increased complexity.

However aside from cost (!), it's just another mechanical approach that we all rely on even for our lives, in many other systems that we use. So if we use it for slowing down speeding vehicles in schoolzones, I don't think it's that big of a deal to use it for actuating or deploying skegs or rudders or (un)fastening hatches or whatever other simple task we could use it for. In a way, many of us already use hydraulics when we blow up our airbags or gearbags in hatchless or hatched yaks.

With skegs(rudders), the big decision is whether to have one. After that decision is made, it's just a matter of the degree of complexity: rope, cable, rod, hydraulic, shaft(?), electric(?).