Sort of... When trading that large a fraction of the whole pool of BTC, the trade itself would drastically alter the value of a BTC. To the point that I'd be surprised if someone could openly acquire that large number of BTCs before being priced out of the market.
The block chain makes it worse because everyone can see the progress of the buyer and there's no market maker with anywhere near this level of liquidity.
A private transaction of BTC wouldn't effect the market value of BTC. It is correct to say 1M BTC = 565M USD; the market price of BTC/USD is only effected when the BTC is sold on an exchange.
Almost no single entity has that much BTC (as of 2016 only ~15 million Bitcoins exist), to acquire it someone would have to aggregate the Bitcoins from many other entities by via buys on a Bitcoin exchange. This would cause a massive spike in the price of Bitcoin.
Interesting to note: there has been no new Bitcoin block for the last 1 hour 23 minutes. This happens from time to time, but it is a little suspicious.
The block chain makes it worse because everyone can see the progress of the buyer and there's no market maker with anywhere near this level of liquidity.