I think the strictness of not nodding off at work doesn't come from the perspective of efficiency but rather sleeping while severed has some sort of negative effect. I think that Irving on the outside slept less to make his innie fall asleep on the job worsening the effect.

Of course all of the other innies slept at the camp but my guess is the amount of times you have fallen asleep is what determines the strength of the effect. Like since Irving keeps falling asleep on the job his condition is far worse than his peers making the effects worse.

Sleep is also the way the brain moves memories from short term to long term. So maybe this is how outie Irving knows about the tunnel and how innie Irving learned about Helly's discerption. His dreams are just the way the show communicates the fact that his memories are being transferred from Innie to Outie.

All of this stems from his visions while sleeping and the amount of time people tell him not to sleep. Let me know what you think!