Would you like an in-game parser?

[Pells]

This is a bit silly. Are they trying to keep the skill ceiling for PvP deliberately low? I can't imagine trying to do arena in WoW without Proximo. 3rd party tools to track battle log info for PvP is a staple for MMOs with PvP. If a program is offering other information, like player position, why not just state that the specific software does violate the ToS, and issue bans for using it?

Because they can be the same program, and SE can't tell from their end which do and which don't without violating some rather serious privacy issues. The logs aren't being used by parsers; they are either reading information directly from memory, or intercepting the data packets. This is because not all combat information is posted to the logs, most notably dot ticks. It's not a big stretch to go from reading damage from memory to reading enemy (pc or npc) positions. In fact, there were threads when hunts were new about just this: some parsers were giving people an in-game advantage by detecting hunt targets before players could actually see them.