I think the implication is different - LARPers may or may not be using a useful technique, but they don't really care about the outcome. If they're sword-fighting, they may use actual sword-fighting skills, but they don't really care if they get it wrong and they get hit - it's just a wooden sword.

Cargo-culting implies you recally do care about the outcome, but you don't know how to get it, and the technique you have is copied poorly from someone else.

To extend things, it's true that if you are about to go in a duel to the death and you are preparing by studying how LARPers sword-fight, you may be Cargo-culting during the duel.