Ok I'm now firmly convinced. I was testing this with Liverpool in a 343 tactic.
My settings:
First notch of normal for width/normal tempo. My closing down instructions start with all out infront to 5 at the back. Timewasting 0. My goal was to make a possession centric tactic, never mind the number of goals scorerd, I wanna play knockaobut footy.
First 15 minutes I was on low DL. Very secure at the back, hardly anything made it past my backline. My mids who were barrowed, were very close to my dcs when in possession of the ball and provided very good support without.
Kept this up for the rest of the first half..made a few attempts at goal, one attempt ruled offside.
In the second half I pushed the DL up to max and scored 2 goals, both from open play. My mids were now leaving bigger gaps between the defense and themselves, so i went back to a low DL. We closed ranks.
The commentary at the end of the match indicated it was "an exceptional half from Liverpool"
There is a direct relationship between the DL and closing down. If you play with a high DL and you play a high closing down game you will be in trouble. You cannot do them both. If you want to play a high pressing game then your DL has to be normal or deep. This will allow your players to fall back into position when you lose the ball.
When you play with a high DL, the mids tend to make their tackles higher up the pitch (relative to ball and their own positon in the formation),. The goal of any tactic has to be just IRL to make the right players close down in the right areas of the pitch.
I hope someone else can verify this,