Nope, not the case at all, rocker cover was in place and gasketed correctly and engine was never exposed to moisture. You need to explore what the combustion products of petrol are and how these may enter engine oil in a worn engine, once in the sump these products can evaporate on hot days and move as gases and will cause rust on exposed surfaces. Also explore how oil responds to gravity. If you leave an engine sitting long enough where does oil go to? I have heaps of engines sitting around and it’s my experienced opinion to check the areas I suggested before spinning them but each to his ownThat thing must have sat with the rocker cover off. I have here the old engine off my 205GTI and it has sat outside for 5 years and it is still oily under the rocker cover. Go to any wrecker and find a car that has not been touched for years and take the rocker cover off. It'll be oily. If the water seals at the bottom of a Sierra engine are not disturbed (do not leak), there is no way water can get to the sump so crankshafts can survive decades without problems too.