There is no way that your character would know that some other character is planning on creating a distraction unless they've told them long ago.
Here's a video of two combat professionals getting into a combat situation unexpectedly.
Count the amount of words they say once shit hits the fan.
And look, they know exactly what their job is and what both of them have to do.
Weird, huh?
Second, limited communication is an aspect of the game. I'm not expecting people to have internally perfected strategy. I'm expecting the players to play their characters without perfect strategy because their characters aren't perfect. If you have time to plan and prepare, great, you can come up with a strategy. But combat is chaotic, mistakes and miscommunication happen. Unexpected and unplanned situations happen. Your characters are actively working with imperfect knowledge and information all the time. For a lot of people, this chaos is part of the fun.
Remember, you were talking about extremely basic strategies or situations like "Should we steal" or "Go flank him".
Finally, one aspect I hate about it, the people who do it the most are either assholes who are generally telling other players how to play their character. A helpful reminder that a character might have an ability or spell is generally fine. But I've seen players bully others into playing the game how they want to play, by telling players how they should react to almost every situation, even if that's not what the player wanted to do.
This is a completely separate issue that has nothing really to do with the situation at hand. And, in fact, only being allowed to ever talk in-character doesn't stop someone from doing this either.