For better reproducing, make sure auto-spotting is disabled in you difficulty options.

1. Create multiplayer game with and play with other player who knows how to reveal.
2. You (the host) be the squadleader and let other player be in your squad.
   • he won't be able to spot the targets for you
3. Switch positions, it will work for both, because the squad will be run locally on other player's computer, but you still are the server.
4. You as the server will be also able to spot targets in AI led squad, but your buddy won't.

For me it seems the problem is somehow connected with locality in multiplayer.

Not important here, just saying that this bug is also in arma 2. (possible ArmA 1 and OFP too, but can't test it)