On that late finish -- that's 18.7% of the winning time. On a hard short stage, the cuts are the most generous. Still depend on average speed. If really fast, can be up to 22% in a typical Tour de France stage of this type.
I didn't find check the race book for the charts specific to this Giro.
This calculator suggests the cut was 18% so the commissaires may have given him a nod, as is their right and in a wacky day like that one with all the rerouting and weather and nonsense they may be more inclined to exercise it. It also points to cuts up to 30% for the TTs. That's a lot.