My observations are;
1 - EVERY Fall when I 'winterize' my race cars, I either drain ALL the coolant out,(including removing the radiator and draining every last drop out of it)
or
2 - I make SURE that my coolant(antifreeze mix) is good for 40 degrees BELOW zero.
Note #1; I NEVER have an engine where I cannot accuratly check my oil level.
Note #2; I ALWAYS epoxy my freeze plugs into the block at time of build up.