but that is unrelated. Automatic transmission fluid isn't circulating through the engine on any vehicle by design that I have seen.
Plenty of vehicles with a standard gearbox just use the engine oil as the transmission lubricant. In motorcycles this is called "unit construction". I've heard of some older Saabs that did this as well.
because the mixing the article talks about it transmission oil and coolant.
When a passageway cracks in a cylinder head & engine oil becomes "milkshake" that is the mixing of engine oil and coolant. Two separate kinds of oil in different places.
Plenty of vehicles with a standard gearbox just use the engine oil as the transmission lubricant. In motorcycles this is called "unit construction". I've heard of some older Saabs that did this as well.