it is true because it is very often that bitcoin has experienced a price increase, the market will also follow up, because bitcoin has become a benchmark price for coins below and for the market too
Bitcoin will remain the market leader for many years if not forever. I am sure that it will become even more popular than now. And the other cryptocurrencies will always follow it.
all coins require bitcoin, but not with bitcoin. so that bitcoin can affect other coins when the price goes up or down. therefore many say that btc is the safest coin, because market movements are preceded by btc