Not sure if the information on that website is legitimate, but to answer your question:
You think is it any danger in whales holding so significant amount of Bitcoins?
Of course there is. Not sure if you can count this as "danger", but whales can significantly move markets by simply dumping their BTC; and there's nothing we can really do about that. This is how open markets work, even outside of the cryptocurrency space. As time goes on though and assuming market liquidity increases in the future, it will significantly get harder and harder for them to move the markets.
It's true that some movement can be caused, but I really think people are overreacting when it comes to the power of 'whales'. For instance, the op is talking about 450k BTC. While it seems to be a lot, it's only 2.5% of the current total supply. Moreover, it's not like 1 person has control over this sum. It's a bunch of different investors with different motives and decisions. That is, of course, if the article is even telling the truth. The real power over the market is informational attacks, leading to chain reactions of panic selling. And it's something that we are a part of, and something that might stop happening often with time.
P.S. Op, referral links are not allowed on this forum, and yours seems to be a referral one.