Thats a very simplistic / basic / fly by numbers approach to windshear warnings. As a previous poster points out, what’s the point of exchanging one windy runway for another with less fuel
Then take enough fuel to have a go and divert to somewhere where wind shear is unlikely to be an issue. That is why you are paid the big bucks! On a normal day too many people take extra fuel for no reason except to make themselves more comfortable (a ton for mum etc) then when they really need loads of extra fuel they add their standard extra fuel!
Time Traveller - I see where you are coming from and yes at some point you may have to make that decision. Hopefully good airmanship will avoid that.