The Aborigines were extremely surprised about too many things.
Just seeing just how they dealt with the half-orc was shocking, to be honest.
Gill and the others being so friendly and not tying up the orc was already inconceivable to them—especially after finding out they didn't register him as a slave—but now they saw little kids fearlessly approaching the half-orc as if it was an old friend.
First of all, instinctive reactions generally didn't lie, especially not from children. From their interactions with the Half-orc, they were genuinely only curious and friendly.
It was far from what they knew about how such creatures interacted in human villages.
Because orcs and half-orcs were so much stronger than humans, they were greatly feared in human territories. If they became slaves, then they were hated, abused, and revenged on for acts that had nothing to do with themselves.