"Skill" with an LLM is nonsense. It's non-deterministic, so any equal efforts are not to be given equal outcome.
not equal, but probabisticly better. Best example: give the agent a tight spec and it will perform better compared with a spec that leaves room for interpretation. This is true for all models, more or less. (purely anecdotal of course)
You could say the same when applied to games with high RNG and chance, such as Slay the Spire 2, and yet those with real skill do perform far better than those without. Those with skill can clear the highest difficulties more often than those with lower skill.
Something being "non-deterministic" is orthogonal to whether or not skill plays a role.