It would make more sense for someone to buy Bitcoin at Baakt and then spend it with Mastercard, although for us it is not a good option. I imagine this is not intended for the average forum user, but for a user who knows little about cryptocurrencies, so buys them at the click of a button from their financial institution, such as Revolut. I won't use it but I guess people who get into this world might use it.
Yeah, I'll keep an eye out for the full details out of interest, but it sounds like it isn't going to be something that appeals to you or me. I'm sure it will lead to some people buying and using "bitcoin" (even if it is not actually bitcoin) who wouldn't have done so otherwise, but the question is how many of these people will then have enough incentive to move away from this custodial not-really-bitcoin nonsense and buy, hold, and spend bitcoin directly themselves.To consider it a currency would be at least in part to recognize the defeat of fiat currency as legal tender in the country, and to waive the taxation of capital gains.
Technically, as bitcoin is now legal tender of a recognized foreign nation (El Salvador), it should already be classed as currency, but of course the US government won't do that. Even just applying the same limit of exempting it from capital gains for all transactions below $200 would go a long way to sorting out the regulatory mess bitcoin currently finds itself in.EXCEPT if you use USDC then they say it's not taxable.
Well, I suppose if your token is pegged 1:1 with USD, then selling it for USD does not realize any gains, and your gains would have been realized when you sold the BTC for the USDC in the first place. Either way, the IRS still want you to pay tax on those gains; all that is changing is when you realized those gains. 
YMMV
