It just an example, no need to be exactly 5.9 w/kg.
I remember about a better example. Col de la ramaz before joux plane in the Tour 2023. They did 5.8/5.9 during half an hour. The peloton had 25/30 guys. This is not hard.
What is the definition of Visma pulling hard?
For me, if Visma let 20 guys in the peloton after doing 5.9 w/kg on soulor during 30 minutes, it is not hard.
If they go really hard, like 6.5 w/kg and only Vingegaard, pogacar, jorgenson/yates and maybe evenepoel together after soulor, then it was...