Gamparse & the 'rogue' rogue

[Arynquad]

Without fail, there is one particular rogue in my guild whose % Accuracy and % Hit stats for Pierce, Slash and Backstab are always shown as 100% in the "Breakdown" column. Literally the only melee/pet that this happens with - and not just in my guild, but on parses where other guilds' melee are being logged.

Even if this particular player has toggled off some melee filters... that wouldn't affect server-side logging, correct? So it begs the question: what could possibly be causing this?