Real quick just to help you out and give you "food for thought"
You have to look at flow and pressure differences in diag. The old headgasket/cracked head is used as a Cover for "we dont know"
So that being an overhead cam engine there is a pressureized oil passage from the block to the head to lube the valve train. If some how the headgasket fail in such away as to connect that passage to a coolant passage then oil would actually go into the coolant as 99% of the time oil pressure is higher than coolant system pressure.
It could be possible that the headgasket failed in away to connect coolant paasage to one of the oil drain passages from head to block that allows oil to drain back to the oil pan. But that is highly unlikely as they are designed to be as far from each other as possible.
Cracked head is possible but rare and when it does happen it is a casting flaw. With "tolerances" being held to tight if there is a flaw like that they dont make 1 or 2 but 10,000 of thousands.
(Ford makes almost 1,000,0000 cylinder heads a month). By tolerences I mean they think they have the procedure perfected and pound them out as fast as possible. If there is a defect they all have it until found. That is why you see recalls that involve millions of cars.
With all of that I would say water pump is most likely casue. It has moving parts that wear. And coolant pressure is easily higher than crankcase pressure.
It is one of those things that would get fixed by accident. "While we are in there we should replace your timing chain and water pump". And no one not even the mechanic is the wiser. He/she couldn't tell you exactly how they fixed it.
