It's basically as I've been saying, the real answer is probably complicated and half lost to time.
Do I think they had a detailed idea of what MI3 was going to be? No, and I don't think they've ever really claimed that.
Do I think they had multiple ideas? Yes, they've said as much.
Do I think Ron probably thought about the story more than "guybrush goes to hell and stan is there?" Yes. I mean, *I've* thought about it more than that, and it's never even been my job to make it, so obviously he had lots of thoughts about where to possibly take it, both thematically and in terms of plot. It would have been impossible not to.
Do I think Ron remembers all the ideas he had for MI3 in 1992 and who he might have talked about them with and in how much detail and what order? No. I don't believe most people are capable of recalling a brief period of their life 30 years ago with that much clarity.
And ultimately, it doesn't matter.
It's not lying to say that he never had a direction for MI3. It's not lying to say he had a basic storyline. These things are compatible because as he's consistently said, the initial thoughts you have don't amount to a story or a design or a direction, they're just a starting point and during the process of creation things become formed.
It's also natural for him to want to downplay the importance of those early ideas because they have become irrelevant in the face of what he's decided to make now. Why would he want to say 'yeah we had all these cool ideas for where to take it' if he knew that if he ever got to make a new MI he wouldn't be using them? The only Monkey Island game that actually matters, ultimately, is the one we're getting.