[*]The orcs just popped into existence instead of rushing down the just lowered gangway from the boat.
While the orcs don't come down the gangway, they are actually running into view from the far side of the boat (a point that is hidden from your view from your current position). The reason they appear to be "popping" into view during that video is because of your perception score combined with line of sight. If you had gotten closer or approached from a slightly different angle you'd see the orcs coming into view sooner.
