taking coin out. if it was on the market (near the market price spread) then less coins means less sell pressure, which actually means less pressure to move he coins prices down
It is not just their coins they withdraw, it is all their funds (we don't see the bank transfers). It also means less orders in the order book (both buys and sells) and as I said above if a whale wants to manipulate the market after that or a "panic wave" starts it would be a lot easier to change the price.