Cap'n. bloggs
I'm with you but that is what the system is certified to , due various factors among which is the integrity of the signals . That is why some build expensive ground augmentation system to get precision approaches . We agree 95 % of the time GPS will get you single meters precision , but in the other 5% you can be off mark and it can be sometimes quite a bit. Fact of GPS life.
I am not saying this is what happened here , no idea , like most of us , but something to keep in the back of one's mind when trying to disregard the approach type as a contributing factor.