My take on flushing water heaters was that they are largely self-cleaning now with the tube going to the bottom of the tank to constantly flush the bottom, avoiding that accumulation of minerals and pebbles from the old days.
Other than that my take was if you are the type of guy who likes that sort of thing then do it, but if you don’t care for those types of handyman chores skip it, and just get a new water heater when the old one goes bad.
Most people just want things installed and for them to work, but if you do drain your water heater remember not to run that hot water onto your grass or plants.
Oh, I NEVER did it. It was just what he told me to do. I sold that house a few years later.
My current house has an electric super stor hot water tank. Meaning, I have a coil going through my oil burner furnace to heat the hot water. Then it goes into a holding tank.
The downfall is that the furnace turns on even in the middle of the summer to make hot water.