I’d change the language around the style.
“Play through the thirds” should describe what you want the team to understand, not ban a useful longer pass. If the opposition step high and the forward has recognised space behind them, using that space can be excellent decision-making.
I would ask players what the longer pass is trying to achieve. Is it an accurate pass into an advantage, or just getting rid of the ball?
That distinction matters more than the distance.
In training, give the players different pictures rather than a rule that every attack must visit three zones. Sometimes the short route should be available; sometimes the direct option should be the best one.
At 9v9 I want them learning a style with choices inside it.
A playing identity should guide decisions, not replace them.