don't agree with what you said I think bitcoin has a low risk where btc is only one and all coins follow it including ETH and altcoins in its network where the price of bitcoin if it falls can be recovered easily not with ETH which follows the BTC value and that takes time long
What you said is clearly true because it happened very often in the past and also at this time when Bitcoin started to decline, for some reason other altcoins like ETH also experienced a decline, even though Ethereum generally didn't have any problems in the market but still fell when BTC is starting to drop in price.