A bad PSU is not at all comparable to a hard reset. A bad PSU can cause individual writes to fail without the entire computer shutting down, and these failures

A bad PSU is not at all comparable to a hard reset. A bad PSU can cause individual writes to fail without the entire computer shutting down, and these failures can and will happen simultaneously across multiple disks since they are all connected to the same faulty PSU. If a filesystem wanted to guard against this kind of failure, I suppose it could theoretically stagger the individual disk write operations for a given RAID stripe so they don't happen simultaneously. (Implementation is left as an exercise to the reader.)