Today, April 20, Huobi has reportedly minted some 4,200,000 HUSD worth $4.2 million.
https://cointelegraph.com/news/huobi-mints-42-million-in-stablecoins-is-it-a-4-20-coincidence
Then the other stable coins will also do the same thing but with unknown dates. The Tether thing started it all and then the others does have the idea of minting since then.
It must be planned about the amount and the date of execution.
That would probably help their HUSD and they like to compete with other popular stable coins in the market, but TBH, I don't know what would be the positive effect of the exchange of using HUSD rather than using USDT.