Yes, it was special, in 20 sec he gave Alaphilippe 5 secs and Bernal 10.
Alaphilippe with cramps rode faster then 2019, when he won.
And yes, Van der Poel went all out on that steep part, because race was on the line, and yes, his time on that part was the fastest of all editions.
I'll give you one thing: Alaphilippe rode as fast as in 2019 from the chicane to the top (44 seconds), but with cramps in this edition, he was fading the moment he got over the top.
So here are the numbers:
2011:
38s steep part,
last K sign to top of climb 1:23, last K 2:17 (Gilbert vs. a group of approx. 25 with Ballan)
2015: 35s steep part, last K sign to top of climb 1:35, last K 2:20 (Stybar vs. GvA vs. Valverde)
2016: 45s steep part, last K sign to top of climb 1:38, last K 2:19 (Cancellara vs. Sagan vs. Stybar chasing Brambilla)
2019: 45s steep part, last K sign to top of climb 1:44, last K 2:26 (Alaphilippe vs. Fuglsang)
2021: 41s steep part, last K sign to top of climb 1:32, last K 2:17 (MvdP vs. Alaphilippe vs. Bernal)
2011 (Gilbert) and 2015 (Stybar, GvA) were faster on the steep part.
2011 was way faster from the last K to the top of the climb.
2011 (Gilbert) was equally fast for the last full K, 2016 (Cancellara) only lagging 2 seconds behind.
Conclusion: 2021 is NOT an outlier in terms of speed on any part of the last K, or you must cherrypick the last 100 meters of the steep part of the climb. That last part was indeed absolutely insane. I reckon Mathieu could have beaten all records by going sooner, and his acceleration on the steep part was probably never matched by any other previous winner, but if you compare the time, MvdP would end even with Gilbert 2011 in that last K, loose 6 seconds on the steep part on Stybar and GvA, and 9 seconds on Gilbert from the last K banner to the top of the climb.