Earl,
Not that any one way is more correct than any other, the way I start my winterization is to connect a water hose to the trailer, remove the anode rod and turn the water hose on at the water supply faucet. That water pressure flushes out any sediment in the bottom of the tank. (flushing is recommended by the HWH manufacturers to remove sediment). Then I turn the water off at the faucet, close the bypass valve, open the low point drains and HWH relief valve and drain the water from the HWH and the lines.
I suppose it would be essentially the same to leave the low point drains open and close the bypass valve after the HWH is empty, I just got in the habit of standing by the HWH watching it drain so I know it's empty. Holding the relief valve, I guess, just gave me something to do while standing there ?????
I also use a pressure nozzle and a piece of rubber tubing to rinse out the bottom of the HWH and then use the same tubing to vacuum out all the remaining water from the HWH. That's probably "overkill" since the owner's manual says the 2 quarts of water remaining in the tank won't cause damage if it freezes. I just like to make sure it's completely empty.
I'd think your method is just as good, just a different way to "skin the cat."