if a coolant journal is blown out on a cylinder jug you would get coolant steam out of the exhaust probably and smell coolant in the exhaust and your compression check would probably show a slight variance on the low side on one cylinder. If he is getting it into the engine oil it is most likely a coolant port blown out near an oil drain port from where the oil on top of the head in the valve galley drains back.
I while back i had a yale F2 engine do that, it was getting oil into the engine oil and blowing steam out of the exhaust too, i had to pull the head and clean it up, check for cracks and check the head surface and the block surface and put on an over sized felpro gasket on it. The block surface where it was blown out had corroded out a place on the block... it was not bad so the oversized gasket sealed it up.
It's been running ever since.

I'm not sure about the toyota engines but some of them even had an oil supply that pumped oil up to the rocker tubes in the valve cover and if this has one it could also be blown out there getting oil into a coolant port.
Hard to say without pulling the head and inspecting it.