yeah, you can only multiply for the inner lists. It's a nice shorthand, but I guess maybe not newbie friendly or something. The actual evaluation of it is:
1. Evaluate the list of one item.
2. Copy the list n times, with the already evaluated value.
So if the thing in the list is a reference type then you've got a list of references to the same thing because what's in the list is references. But that's fine for tiles, because with tiles you are presumably not mutating them all the time.
In any case I'll just add that the BGT tutorials aren't very good. If you're willing to read sighted game programming guides you can get more info than those by a lot. The real problem is that people assume audiogames are different when actually they're sighted games but we just don't add the graphics code.