True or not, whales exist on other market as well. The only difference is that in crypto, we only have addresses, with no associated names. So all we can do is speculate it indeed they exist or who owns that huge amount of bitcoins. There are speculations as well that they do connive with one another at some point to bring down the price so that they can accumulate more.
You're definitely right that whales exist, but there's no way to identify them. This is one of the reasons why bitcoin's price is tagged as manipulated and controlled by other experts. It's so impossible to prove their existence, however we can prevent further damage cause by manipulation if investors would not panic every time there's sharp decline.