Ordinarily, that would be through creation of an account on the company's server, which is hackable. For 21, authorization to access service X might be a function of a 1 satoshi transaction to the 21 servers from the BTC computer.
The latter is fundamentally less hackable than the former how exactly?
Sounds like smoke and mirrors to me, or an attempt put some sort of new spin on a fairly routine business (running a server to process transactions) in order to justify a higher valuation the way companies like Square claim to be doing "payments innovation" but they are really just signing up merchants and getting credit card processing commissions (i.e. smoke and mirrors also).
Sounds like a centralized payment system that is superior to the old centralized payment system primarily from the perspective of someone who manages to place himself at the new center.
One use authentication through blockchain transactions, the other through login/pw
