honestly, i think that it isn't much of a plot hole because i mean in this case, Oda just has to mention something like on a side note that could be done anytime, like i mean Jyabura mentioned that there are demons inside the fruits themselves so we have that much
like it could be that the demons leave the person once they die and manifest into another fruit, i mean, personally, i think Oda needs like an entire arc dedicated to the DF because they are still such a mystery in their entirety, i know that it adds to the suspense in the series, i think they might just have the arc since they've already mentioned Dr. vegapunk, which could be like the next arc after Brooke, so it could be explained that way,
i think the only other real plot hole could be the fact that DF users can't swim, it might have been informed why but, if so, i forgot it, so correct me if i'm wrong,
also, this is not really a plot hole as much as it raises some questions but would a logia style DF user with power over water (including salt)(i think they might have mentioned it in their possible DFs in the first few episodes) lose the ability to swim and, thus, be able to drown?
I\'m like Neo but better,cuz I actually know Kung FU and I can kick ass