A failing head or gasket will start by letting combustion gasses into the head and as it deteriorates further coolant will start seeping into the cylinder post shutdown as the residual engine heat will push the coolant perhaps 20° to 50° over shut down temp as it heat soaks and cools. This heat will drive coolant pressure well above normal running, and is how the nominal 1-2 bar coolant pressure could get into a high compression cylinder @ 18+bar. Now if the compromised cylinder is in a power or exhaust stroke when shut down the errant coolant will be exhausted and you will be no wiser, but if its on an intake or compression stroke and there is more than a combustion chamber volume of coolant it will lock up and it seems the starter will maintain the current until, key off, the start cycle times out (30 sec I think), the coolant lock seeps past the rings and back to the coolant system and the engine starts, or it self destructs. Though for his scenario to be true the engine could only have cranked for one revolution maximum and then it stopped cranking abruptly whilst the current continued to toast the starter.
This is starting to sound like a cracked or porous cylinder or cylinder head!
