A glimpse of Ben's True Strength
( The high demon's POV )
The high demons within the demon camp did not patrol.
High demons in general were treated as first-class citizens within the demon world while the common demons were second rate and hence high demons did not participate in repetitive and laborious duties like the common demons did.
This divide between the high demons and common demons was not because the demon society was racist, but simply because the high demons were physically and intellectually much superior than the common demons.
On average they were 4-5 inches taller, much more muscular and had heightened body functions such as a sense of smell and hearing.
And it was because of this heightened sense of smell that the high demon was able to smell-out Ben and Leo from a distance without even seeing them, as unfortunately for Ben and Leo, the wind carried their scent downstream for the demon to smell.