Not to brag, but some people said they could imagine the rides I was describing for them (they are not on this forum as they are not Disney-themed). I guess it is up to you, some people find it easier to get a picture in their mind of what you tell them.
About the alternate reality... I kind of explained it because I wanted to and you can do that as well if you want to. You don't "have to", you can if that's something you want to do.
The fact is, I'm not used to admitting that my ideas are set in a place not of this world or something. I like to try to set my ideas in the real world whenever possible. That's why I need a disclaimer, so I can at least be honest that this is probably not going to happen. Can you or anyone else think of some good words to use to describe the park's fictitious nature?
What's more, if I set in an entirely fictitious area, one not of this world, I'm pretty sure I would have to explain that area not of this world first in as much detail as possible. In other words, I would have to do some worldbuilding, and I'm not too good at making things up. It's difficult enough to do a park in a real-world location, never mind inventing a whole new world to go along with the park.
For instance, I had at one point thought of making up an entire city somewhere, possibly in Brazil, and mixing it with Berlin to call it "Berlisilia" (a merge of Berlin and Brasilia), but that would require a ton of background on the city itself before delving into the park. What's more, what language would it be? Portuguese? German? I don't believe there has ever been a park, Disney or otherwise, that has ever used more than two languages in a park. It's usually English and the language of the country it's in, but that's it.
So as you can see, I need a disclaimer to admit that my ideas are fictitious (because unlike a lot people here, I don't automatically "get" it without any help) and I like to be as realistic as possible and deviate too much from conventional wisdom.
Also... "how can you see something if it doesn't exist?". How do you think actual imagineering works? I think that it must be something like this: a group of people gathers and gives suggestions. Then they have to "see" those things in their mind so they can draw them on paper and work on the more technical aspects.
The problem is that you can't really "see" anything in your mind. The only way you can truly put it in visual form is to maybe draw pictures. Or better yet, perhaps use Roller Coaster Tycoon or Planet Coaster or something. That way, you can at least see a visual representation of your idea. After all, don't Imagineers draw pictures, as you said?
I'm not really the best drawer of pictures, I'm sorry to say. My drawing skills hadn't improved much since high school.