No, it's easy to get to. I've been trying to understand it as well. He's not a full time tractor mechanic, but he does house calls. I think he was being extremely conservative.
I had oil spewing from this port the instant I started up my tractor. I'd been snowblowing on fresh snow the day before, so I know I hadn't dripped so much as a drop yesterday.
The manual says it's the "main gallery access port" and nothing else about it. I looked in the engine parts manual and...