It is clear from that thread you rate Dawson a hell of a lot higher than I do. I like him, I really do, but it seems to me you rate him as some sort of defensive GHod!
Athletisism is a big part of the high line, IMO. Ability to get into positions to cover runs, and yes, dash back when you get beaten.
I dont see Dawson as having the pace or agility to make it really work.
It is also about anticipation, sensing dangers and stepping up to clear them before they really form. In the King/Dawson partnership for example, King played this role - I do not believe Dawson has it in him.
He is at his best as a reactionary, body on the line, blood and guts kind of defender. In this respect I think he is fantastic, but I also think this sort of defender is simply not what is required for the role.
Look at Caulker, Gallas, Vertonghen and Kaboul, they are all either very athletic, very intelligent/ball playing types or both.
It seems to be a definitive theme we are looking for in our CBs and Dawson stands apart as a very different type of player.
Genuinely I do not believe it is a power play by AVB, Dawson is a model pro and would do anything for the club - he isnt a Terry like tumor to be cut out. I think its nothing more than AVB looking for a certain type of player and Dawson not fitting the requirement.