NPCs start combat with werewolves from any distance
The aggro distance of humanoids when you are a Werewolf feels way too high. I am constantly in combat with NPCs that are so far away I cannot even see them.
Standing on the rock next to Brandr and Erna the Quiet, the NPCs in front of the house to the west do not aggro. You have to go past the middle of the river for them to engage. Second picture shows the distance from which they will enter combat with you in OpenMW.
Here's going around the corner outside the walls of Fort Frostmoth, the Argonian shipmaster Basks-In-The-Sun will not aggro in Morrowind but does in OpenMW.