I did not explain "why" because I do not know! My opinion is based on my personal experience and other's too. As said, I do not play 4-5-1V agaisnt 3MC oppo. This season, I faced 3 or 4 times 4-3MC-1-2 with 3DC-1-3MC-2WAM-1 for as many victories. Maybe I woud have won with 4-5-1V too but I had too many bad results in this case so I prefer being safe than sorry. Some counter tactics are logical some are less. For instance, I have played maybe 70 or 80 times against 4-4-2 classic and lost only twice with 4-5-1V. And this is not completely obvious when you look at the formation themselves. It should be a closer match as neither tactic shows many weaknesses.