I think this is a rather straightfoward cap. See it like this
roughly) if X is the chance that you are currently ahead then 1-X is the chance that you are currently behind.
Then our equity at the turn is (let's ignore his outs against us for a while), lets say we have roughly 10 discounted outs. Then our equity is about
: X + (1-X)*0,2 = 0,8*X + 0,2, i.e. if X <u>></u> 37,5% then we should 3-bet (roughly).
This criterion is easily met. I think it is strong enough that overturning principles (i.e. he might fold to a 3-bet but call a river bet or whatever) will not influence our decision.