Well, yeah, of course, you need some limit on the speed at which the power supply voltage drops, I was talking about the "flushing the cache" kind of "power loss protection", not claiming that pulling a circuit into the reset state could happen without latency ;-)

So, yes, you of course have to have some low pass in the power supply rail to make sure that power drops no faster than you can handle shutting down the circuit in an orderly fashion - all I am saying is that there is no need to guarantee that a read of a region where a yet-unacknowledged write was happening when the power supply failed returns non-random data, so it is perfectly fine to interrupt the programming process and leave cells where user data is stored in an indeterminate state. It's not OK to glitch address lines while programming is still going on, of course :-)