I don't disagree with that but if you see my picture with oppo formation, I had to face 5 possible attackers. The three ST and maybe the MR & ML from the flanks if playing with red arrows, that's why I set 5 defenders.3dc will mark all Players in the 5 Defending positions. that means the left dc will mark Player in dl, left dc and middle dc. not only this positions. they will mark Players in dml, dmc left and dmc Center, too.
Also I 'm sure that 3DC have a disadvantage vs 2ST and AMR-AML or even vs 1ST + AMR-AML playing from the flanks.
I realized about zonal when I was trying to beat 3 def. playing wide (probably with zone) with a 4-4-2 ND, but couldn't do sometimes
- but usually I think the game gives some kind of advantage.