I'd wager that if a manager says that they want you to take it more like a real marathon and less like long hike.

In a marathon, not sprinting is the rest.

There is no rest. There is just (properly done) a continuous output from start to finish, or a very slight increase of output (negative splitting), but effort to maintain it feels exponential. In terms of feeling, it’s a 32km « dynamic run » where you should feel good, then the hardest 10k you can pull off just after that. If paced properly there should not be a « wall » but at all levels you pass people walking who disintegrated around 30km. Even people with sub-elite/elite bibs sometimes explode.

A half is more intense but way easier, you’re just sub threshold but for a time short enough that you cannot really not make it.

No its not a rest, marathon runners are still exhausted at the end, they can't go and run another marathon right after.