Mark CMG, you've slightly misquoted me. The phrase from which you've extracted that quote reads:
In the phrase I actually wrote, the pronoun which refers to the dimension of significance. As you quote me, though, you create the impression that the pronoun which refers to player choice.
So you create the impression that I was talking about encouraging one particular player choice - ie railroading. Whereas the point I was making is that different approaches to writing an adventure open up different dimensions of significant choice. The three dimensions that I contrasted were those of operations, of tactics and of moral/political allegiance. I'm sure that there are other dimensions to be identified also.
An adventure doesn't become a railroad because it makes one or the other of these dimensions more salient.