No it is true, because when Pog and Stuyven attacked Vingegaard and Roglic were already held up with misfortunes. We have no way of knowing had they been with Pog when he attacked, and the surely would have if they hadn't flatted or crashed, if he would have dropped them.The stage was 10 km too long for them it seems. But your last sentence is not true. During most difficult cobble sections Pog and Stuyven were strongest and fastest of them all (including JV collective efforts).