In my opinion, 422-31(b) allows a breaker which can be locked to be the disconnect switch. What you have to know is what does your inspector believe is a "lock". Is a breaker lock a lock? Or is it not really a lock because anybody with a screwdriver can remove it. The code does not define what a lock is, that I know of.
This section covers permanently connected appliances over 300 VA, which would be required to be used in the instance of a non-accessible cord-and-plug connected appliance as per 422-32(a).
So I personally think a breaker lock is a lock and the breaker is allowed as the disconnect.
Now also take into consideration 422-35 Exception. Is the switch at the counter top for a disposal a "unit switch"? If so, then as per 422-33(c), assuming a single-family dwelling, if the house has a main disconnect another disconnect is not required.
If not, then it is considered the controller and a disconnect is required for the controller and must be in sight of the controller as per 430-102(a). So I guess you would have to install two switches next to each other in a double gang box. Since this seems redundant and most people would have a fit about two switches that disconnect the same appliance in essence, one switch with a properly labeled breaker would be ok with me.
This question can be tricky, but I think good common sense should be used and the risk of injury can be avoided.
