I'm not sure that Alaphilippe burned much more cartridges than the others :
As Voeckler explained in a post-race ITW, this time Alaphilippe just sat up whenever he looked back and saw the whole group together, which meant people were still there to work for their leader.
For every attack except the one where colbrelli went with him, the others spent energy trying not to get dropped, and in that kind of climb, not much is gained from being in a group. Come the flat part, Alaphillipe is already caught.
1st attack @58k : Wva, stuyven did probably the same effort as JA, because they took turns after the climb.
then Remco drived the group, with Wva sometime behind him ( so 30% in the wind
)
2nd attack @49k : This time Ala did a bigger effort than Wva, only colbrelli followed him. But to catch the 2, Wva and stuyven took turns so overall they also used energy.
then Remco again on the front, and ala talking with the Voeckler.
from 27 to 23 some accelerations but Ala stayed in the back and was probably able to have a more constant pace.
3rd attack @21.7 km : Madouas hits the afterburner and drop everyone but Ala. Wva starts the climb at least 8 m behind the two frenchmans, he almost catch up before Ala goes.
I'm not sure Ala burned more energy than Wva for this attack.
then people took turns with Ala before the last attack :
4rd attack : @17.4km : no one seems to try to follow him. Some people go but maybe not the strongests (Pidcock, Colbrelli).
at 10k, only 10sec, they maybe had a chance to catch him, but they attacked each other instead.
To me Ala was the strongest, but maybe not that much. Maybe Colbrelli, Pidcock, or even Valgren could have stayed with/catch him if they raced differently.
Some of the strong guys only watched on Wva and Vdp to do everything, and that cost them at least a medal.