Say if the anti freeze does freeze. In a full, closed, system the water expands and with no where t go, can cause damage. In a system that is 1/2 full, anti freeze in the system, the expansion has a path to expand, not causing damage. .
This is not true. I WOULD NOT leave water in the block under any conditions If it does not have or doesn't have enough anti freeze, drain the block. You MUST remove both drain plugs, one on each side on a V8