For example, there's been at least one high-profile plane crash in the past (Lauda Flight 004) where a thrust reverser (diverts the jet output forward instead of backwards, used to slow you down quick during landing) deployed mid-flight. That should have been recoverable, but turns out Boeing only projected outcome at low speeds and altitudes. The outcome at cruising speeds/altitudes turned out to be far different and the plane went down.
While cruise wouldn't be an issue (don't think they get up that high!) I'd expect the outcome of a drone hitting a flight control surface might vary between takeoff, landing, and lowish-altitude holding.
Control cables would be a concern but hydraulics and fuel aren’t typically going to be a concern. Fuel isn’t as combustible as everyone likes to think. There are also additional tanks. Hydraulics offer redundancy on aircraft that use hydraulic control surfaces.
I’ve seen a Cirrus SR20 hit a deer at takeoff speed and leave a 2.5 ft hole in the skin of the wing the went as deep as the reinforced fuel tank. The aircraft continued flight and came back around and landed just fine. Even flew to the repair airport after cleaning up some loose fiberglass.
Personally what worries me more is what would happen if they fired this thing at the plexiglass windscreen. In a GA airplane that would likely be fatal.
They are under load, it's like taking out a bunch of columns at the ground floor of a building. Not to mention that wings are full of fuel, as well as the cables or hydraulic lines connected to the control surfaces.