The way I understand it, there is a small area or zone surrounding every character and npc. If you leave that area, it prompts an AoO. Thus, if you are careful not leave the area in your attempt to get behind them, you can avoid the AoO. In other words, I think it is working as intended. Now, whether or not trying to get behind someone should trigger an AoO is another matter.
in D&D as long as you dont leave THEIR melee range you're fine. The issue is them leaving the grid system. The spears have a range of 8.3 feet, glaives 10. Its all over the place. The character models arent exactly elegant in their space occupation and the pathing decisions for avoiding terrain will frequently bump you out. Its life when you dont know a dragon has a 20 foot bite range, but a lot of this stuff is just poor execution. I found a bug where if you leave the range of a mud mephits mud ball - 60' - itll throw one at you from across the level. They just generally need to tighten it down and give better char movement. Its so critical and in D&D players and DMs spend a significant amount of time jockeying for position. In this its a "welp. guess im goin in!"
