There are situations where there is no guard at all, and there never was, due to flawed generation. This item was added for that reason.

That's correct, but I specifically emphasized the shifted guard. It's already clear what happens when there is no guard.
Point 5.6.3 needs to be rewritten as follows:
5.6.3. In the case of no guard at the passage, it is allowed to freely move from one zone to another.

If left as it was, this point allows the following (I will break it down into two, so my point is clearer):
5.6.3. 1) In the case of no guard at the passage, it is allowed to freely move from one zone to another.
5.6.3. 2) In the case of a shifted guard, it is allowed to freely move from one zone to another.