That said, it's weird for an exchange that claims daily volume trading in billions to look for funds to borrow from customers at these rates. Promotion, yeah maybe, a publicity stunt, you might be right and everything is actually harmless but afters years of unfortunate events in the crypto environment I'm looking with suspicion on everything, especially when it comes to a way of earning money doing nothing.
it's pure gimmick IMO. they're just riding the defi train---everybody wants to get paid interest on their crypto now. it's just a marketing ploy to ride that wave and snag some new customers. coinbase is doing customer loans now too for the same reason. it's mainly to get customers to lock up their funds at the exchange, which probably makes them much easier to retain as trading customers.
huobi also provides centralized margin lending---charging 0.0980% daily interest rates to traders at this moment. compounded daily, this is more than 10x the effective annual rate they are paying out to lenders with this "savings" account. if they are using this mechanism to provide liquidity for margin funding, then it makes sense. binance does the same thing and just stops making new offers to borrow when there is too much lending liquidity.