Sometimes you think you're not "working" but you are thinking about your work. So you "work" 2h/day by really typing and coding and so on, but you think about some problem another 2 or 3h/day. So you have to consider that, too.
The situations I am aware of are very far away from needing to spend 100% or 200% of their actual working hours in thought for the implementation and / or strategizing.
I haven't worked in deep tech, or cutting edge, so it might be attributed to this.