Learn something new everyday!

The one 6.4 that I worked on, really did have a 3 bolt
tone ring

It was a pre-production mule that had been rode hard and put away in a basket, and I've only rebuilt that one....no production engines.

I'm going to take a wild guess:
Maybe whoever was on that chat session saw the engine around the same timeframe as the one I saw, and they assumed it didn't change...

At any rate: oopsie...

Summary:
I'm glad you didn't ask me, I would have told you the same thing