They don't really. They are just affected by what bitcoin is doing. If bitcoin price is changing they always get dumped. And whenever it is stuck in a fixed price like these days the shitcoins start pumping simply because there is no profit to be made day trading bitcoin at a fixed price like 34k but a lot of profit to be made in shitcoin pumping and as soon as bitcoin starting moving they dump those shitcoins and come back to bitcoin; which is why altcoin always dump when bitcoin moves.
When BTC goes up Alts on the BTC/ALTcoin chart dump but On ALTcoin/USD they go up ... just not as fast as BTC do. Depends on market condition.
My post was not wrong either. When I expect high volatility on BTC very soon (like the day when I wrote my post) I call TA on altcoins useless. As we see today, BTC broke support and everything is -10%. If something did not drop means it is not actively traded. If BTC would pump 10% alts would pump at least 5%.