Well, I understand what you meant. I will consider if there are only 3-4 complaints that happened back then (the year 2015) about 999dice.com scam incidents. But there are a lot of them complaining against that gambling site.
Indeed, I did not see any resolved issues at 999dice.com. Well, as what theymos said.
Seems pretty plausible, though you're right that it can't be proven. Still, people should stay away from 999dice.com until they change the way they deal with seeds to rule out this sort of tampering.
But this is precisely what I'm pointing out. it clearly says the way they dealt with seeds was the issue back in 2015. But that issue was fixed. I can't remember when but not later than maybe mid-2016 cause I remember that's when I first came across the issue in that old thread, and by then the seed system had already changed. I'm all for calling casinos out on bad practices, it's our duty to do so! But it's annoying seeing people reference an issue fixed over 3 years ago.