I'm not saying its impossible to achieve technically, just that there is a whole fleet of installed equipment and the comment I responded to made no mention of unsafe temperatures...

Unsafe temperatures happen at 42C. Pasteurization starts at 50C. A water heater that stays in the 60 to 55C range I mentioned never leaves the safe zone.

But further, once pasteurization has occurred (which takes 2 minutes at 60C), Abiogenesis doesn't happen. A water heater can safely go down to 36C after it's hit that 60C temperature. Not that it would.

So long as your water heater is hitting 60C once a day and stays above 42C, you have very little risk of developing dangerous levels of Legionella in the tank.