Binance has holdings in all sorts of cryptocurrencies that it has no involvement in the creation or minting of.
As a cryptocurrency exchange, Binance must hold Tether to operate.
As the most popular cryptocurrency exchange on the planet, they're likely to be on the larger end of Tether (and various other cryptocurrencies) holdings.
I'm not defending Binance here, I think there's fair potential that they're doing shady stuff, but they're not responsible, in any way, for the minting of billions of dollars of Tether, or involved in any of the dodgy accounting around Tether's backing.
Same goes for Huobi, who are second on that list. They're an exchange. Holding Tether is an essential part of being in that business.
Binance has its own stablecoin: BUSD
USDC is associated with Coinbase, the exchange that recently went public, so I'd assume it's far more trustworthy than Tether.