No. I think that a thesis proposal is an outline of what you think from here you can do, that satisfies your committee. It may turn out that, in the process of writing, the path that you end up taking turns out to be rather different. If it's very different, of course, it has to be cleared by your committee, but because very often you are trying to give arguments which you hope will work, and then you get to the point where you give them and then they don't work, you have to change ... what you're doing, because you wanted to prove something that was impossible.