In this artificial setup, White pokes at Black's compromised diagonal. If Black doesn't act, White can push through at a and cut off one of the black stones.
When evaluating this board, KataGo doesn't think this situation is urgent and prefers a move in the corner. Black would then be behind by 1 point, which is our reference (in the settings used, Black starts off at -0,7 and lost 0,3 in these first 6 moves).
If we take the last option as a net loss of playing at the center, then we can estimate the choice for a farmer's hat shape as a 6,5 point loss.