In Burning Wheel, or a similarly-structured "say 'yes' or roll the dice" game, the decision heuristic would be along the following lines:
*Is there anything at stake in looking for the high ground/overwatch position? This would depend on at least two factors: (i) what is the current state of the fiction - eg does looking for the high ground imply leaving the rest of the band, and does that have meaningful implications? (ii) does the sniper have a relevant Belief, Instinct or similar (eg Instinct Always take the high ground or Belief I will be the overwatch!) that makes this meaningful the character?
*If the answer to the above is "no", then say "yes" as you did.
*If the answer to the above is "yes", then call for an appropriate check to find the position (eg Perception) - depending on further context of play and character priorities, it could be done as an initial test to identify the ground, linking to a test to actually establish a position (eg that could be a test on Tactics with Stealthy FoRKed in). A failure on the Perception test could be narrated in different ways - maybe there's no high ground (so the PC has to stay with the band) or maybe the character sees the high ground but it's hard to get to, or has a zombie guarding it, or something else fitting and cool.
So between your actual example, the easily-sketched way it would play in BW, how we might imagine it playing out in Apocalypse World (the PC looking for high ground would be Reading a Situation), how it would work if playing The Punisher in Marvel Heroic RP (ie establishing an Overwatch Asset, by testing against the Doom Pool augmented by any appropriate Scene Distinction). etc - we can see pretty easily how the OP idea works out in actual RPGs that don't just assume GM narration in accordance with GM aesthetic priorities.