I partially disagree with this. I have studied prices of coins and tokens on CMC and the fluctuations of each currency seems to be unique and independent of any other digital currency. Some show strong pumps when BTC goes down and some heavy dumps when BTC is rising.
Undoubtedly, there are market forces and factors which affects most currencies, this is not influenced by bitcoins price, it rather controls bitcoins' price as well as others.
So when trading or investing, make sure you treat each currency differently as they have different utilities.
Its not the Bitcoin itself who controls the market, but of course it is still depend on the demand of the investors in it. Since bitcoin was a volatile we cannot says what would be the volume of it. Same goes with altcoins because of the volatility there are two things may happen always in the market which is Increasing and decreasing value.