The hustle exploration activity can only be used for [con mod x 10] minutes at a time, but given that it doesn't cause fatigue, can I assume a character can take a quick break and resume hustling?
On the one hand it works better for long-distance running, but I wonder if hustling for effectively the entirely exploration day was intended.
Speaking of exploration time, it seems like the rule that a party is fatigued after 8 hours of overland travel (in ideal conditions) should be listed in a more upfront fashion than being hidden in the temperature effects table. I read the line about precipitation reducing non-fatiguing travel time to 4 hours and spent an hour flipping through the exploration sections trying to find what that 4 hours was reduced from.
Personally I wouldn't throw fatigued on, I would simply not allow more than that amount of hustle per day.
Fatigued is incredibly punative and would just result in the party going "well we stop at 29minutes" or not using it imo.
As for long distance runners, they aren't carrying PC like equipment over natural terrain.
It may not seem like it, but even the simple act of jogging in heavy boots and having some light gear strapped to your body would make travel a lot slower/more laborious over uneven natural ground.
So yeah, for a con 18 character it would just represent that they can hustle for 40 minutes out of each day if they wish.