Fraud isn't something you can worry about after the fact. There are strict regulations around anti–money laundering and counter-terrorism that are less about de-frauding an SMB then spinning up fake businesses and using payroll as a conduit. The challenge with blockchain payments in payroll is anonymity and irreversibility (two of its significant differentiators.)

At that point, what are the benefits? Transaction speed is one, but you only really get that if the business pays in crypto (otherwise you still need to wait for the ACH payment from them or float the money (don't float the money.))