Writes are completed to the host when they land on the SSD controller, not when written to Flash. The SSD controller has to accumulate enough data to fill its write unit to Flash (the absolute minimum would be a Flash page, typically 16kB). If it waited for the write to Flash to send a completion, the latency would be unbearable. If it wrote every write to Flash as quickly as possible, it could waste much of the drive's capacity padding Flash pages. If a host tried to flush after every write to force the latter behavior, it would end up with the same problem. Non-consumer drives solve the problem with back-up capacitance. Consumer drives do not have this. Also, if the author repeated this test 10 or 100 times on each drive, I suspect that he would uncover a failure rate for each consumer drive. It's a game of chance.