An optocoupler will isolate the communications themselves, but perhaps he was referring to the fact that the overvoltage 'crowbar' circuit would need to be software controlled. Overvoltage protection shuts down the power supply when the output voltage rises too high - say if the FET gets stuck on.
OTOH one could put additional protection downstream in the load itself, and the PS would just need a well-known fixed overvoltage. If the "5V" PS started outputting 15V (but still under the PS max), the device would just shut down. However, don't expect manufacturers to do this on their own - as the article says, $1 is "expensive".
OTOH one could put additional protection downstream in the load itself, and the PS would just need a well-known fixed overvoltage. If the "5V" PS started outputting 15V (but still under the PS max), the device would just shut down. However, don't expect manufacturers to do this on their own - as the article says, $1 is "expensive".