The most curious thing this year was how 36 year old Thomas was significantly quicker on the Alpe than the 32 year old Thomas who won there in 2018.
Could just be how it was raced. In 2018 Thomas followed the wheels and was fresh enough to ride away from everyone at the top, so could have gone faster. This year he hung on to Vingegaard and Pogacar for a good portion of the climb and the rode his own pace...
Also, the wind can make a fair difference (no idea what the conditions were like either year).