I don't play other games so I can only couch my contributions to the discussion through the lens of 5e (well, except for Worlds without Number... but adjudication is largely the same as in 5e... or maybe we're playing it wrong... lol)
So are you saying the goal of distracting the guard is ancillary to the goal of hitting the tree?
Hitting the tree is a success on a good roll, but you have no way of distracting the guard? Distracting the guard, to me, seems like the real goal/intent of the whole exercise.
There are other things the PC could try:
Player: "My PC uses ventriloquism to cast her voice over yonder to distract the guard"
DM: "Ok, roll for it!"
Player: "High roll! Yes!"
DM: "You successfully cast your voice over yonder! The guard is unfazed."
That... is a most unsatisfying outcome. IMO. I'd be like "wtf"? Is that something you'd honestly tolerate as a player
@Hriston? Rolling a success an not achieving your intent?