Splash?

So splash allows your other positions to gain LP while they're still in placements. So if I just play on my main role and gain splash, I can technically skip 7 promotions (1 game to start placements and the other 7)? Since you don't lose LP, that means that you can continue to play those roles and would only need to win 1 game to gain an LP boost and go up?

Of course I know that it would take 20-40 games for splash promotion, but it's just a thought.

Edit: Assuming majority of those games are wins