That's preposterous...
I reached level 30 in Preseason 5, which was still technically counted as S4 by LolKing. As almost every other person, I was placed in Silver at the end of my Placements, but I didn't really deserve it. Proof being that, as soon as S5 started, I got placed in low-Bronze, then progressed from Bronze to Silver during S5. And then I progressed from Silver to Gold in S6. But sure, that's a pretty big and sudden "jump of skill", just happening over 2 years...
Oh, you can also check my OP.GG if you want, it will show you that I only played 2 games in a Duo recently, that I lost both of them, and that I still have a 11-9 record. (And in fact, it was just a random guy that I happened to be matched with 2 times in a row, in early morning.)
I'm not one to hide that I regularly play in premades, and I've been pretty open about it and about defending DQ on these boards. But calling me boosted after actually checking my stats, not just as a baseline insult, that's kinda ridiculous... If you do fact-checking, at least do it properly.