Why not use a stablecoin? Or are they dealing with Bitcoin volatility in another way?
It has the significant disadvantage of adding an additional trust entity (the backing bank) which could prove untrustworthy.
Over a long enough timescale, I would argue that all backing banks have proven to be untrustworthy.
All forms of money have risks. I think the diversification of supporting BOTH USD and BTC seems to get a bit of the best of both worlds.
USD-denominated stablecoins have the union of the risks and disadvantages of both.