We know that a cold wallet is always safer than a hot wallet, because only the owner of a cold wallet can access the wallet with a hardware product, and the wallet will always be safe while the hardware is offline. However, hot wallets play a more important role in the crypto economy, because trading is the best way to determine or verify token prices.
In the Kucoin case, I think this is just a hack, not an exit scam. KuCoin is too famous and they won't lose their credibility & exchange just for 150M USD.