Yes its not US dollars. Its USDT - tether - stable coin pegged 1:1 to US dollar. Crypto deposits, crypto to crypto trading, crypto withdrawals does not need KYC on kucoin but if you want to deposit/withdraw Fiats kYC is mandatory on almost every platworm. P2P trades are all you have if you want to avoid KYC and use fiats. But after you buy USDT somwhere, you can deposit it to kucoin and trade ... but i do not recomend that, as Potato Chips said:
One day they will lock you account saying - "we've recorded strange activity from your account" or something like that and they will force you to do KYC. Just like binance locked my account 2 days ago and asked for face scan (i did ID KYC 2 years ago ... now even this is not enough).