Basically, if you really have a big volume of coin you might affect the price of the coin in the market. I believe that it is not manipulation but jist a short term effect on the coin's value. Surely in no time tge price will eventually recover and continue to go on it's way. Changes might happen but no really haa the full control over it.
Agreed, someone with a big stack could just be selling and influence the market, but does not mean he is trying to manipulate the price.
Yes, some traders can change their mind when trying to make an order, but the truth is that a lot of manipulation is done in this market, and most traders would definitely have noticed that.