While you may dismiss the first three, they all had the same pattern, including his victory.I don't disagree with your premise that you can't claim someone would have easily won a GT when they DNF halfway the GT.
But saying that Remco has a history of looking strong in the first half of a GT and failing in the last week is a big stretch to me.
His first Giro does not count imo. I think everybody agreed (at least in hindsight) that it was a bad idea to even start that Giro considering his abysmal and rushed preparation after his crash.
He won his first Vuelta and had to leave his second Giro because of Covid while being in the leader's jersey. That leaves only his Vuelta this year where he failed in the second half but one failed GT can hardly prove a 'history' of failing in the last week.