True that this could be a possibility but I haven't heard/seen any kind of hacking/bug that can modify rAthena's server setting especially drop rates.
But if there is then well accepted--else, please do something about this person, he is simply not doing things accordingly.
I'm not pretty sure how this post can be moved to the international forum.
Just to reference the link above (the said post was already deleted by the server owner)
here it is: