Agree. The main reason to not let water freeze in your system is to prevent expansion in restricted places, like pipes, with the possibility of bursting them. Small amounts of water in a large area like tanks will not hurt a thing, unless it gets down into a pipe or valve where it cannot expand. When I drain, I leave the valve open for a day or two to make sure that all the water that can reach the drain hole is gone, and then close the valve.
2003 Ford F-350 V-10 Crew Cab 4WD Long Bed
2004 Jayco Designer Medallion 29 RLTS 5th wheel
Bill, Gayle, and Mindi (dachshund)
Retired at last !
Nothing is foolproof to a sufficiently talented fool.