While this is considered a problem in PvP, perhaps it may be worth identifying how this affects PvAI? I presume that the AI will 'look' from where the hitboxes are supposed to be, rather than where the model appears. Additionally, are we certain that the AI can't "see through" the grass anyway?
I think that, at least until a proper fix can be made, model-sinking should be disabled (maybe leave an option for it?), as it makes shooting at nearly all ranges very inaccurate.