The ford manual does state 1 year warranty on factory alignment, but also it also states warranty void on modifications.
1. The fact that when Thor gets the unit they have someone cut and stretch the frame (as JamieGeek points out) voids Fords alignment warranty. Stretching doesn't change it, but weight changes with the extra steel does.
2. After Thor adds the house, the weight shifts again.
3. You load it up - small but weight shift again.
All this change in weight over the suspension pushes down and changes camber / toe. It may change it only slightly. But When Ford aligns the bare F53, they set it within a range (tolerance). They are not all set exactly the same. So, after all the weight change, if you were in the middle zone of the range, you may end up still aligned within tolerance. But if you were on the edge of one of the tolerances, then you may now be out of alignment, as many people have found out.
I spoke to Thor and was told, they do not align the the class A units due to many variables of what the owner may do in terms of weight. The Thor rep at warranty services told me they highly recommend you to get an alignment. It's just another maintenance cost.
I took it to a local tire shop whom did the alignment for $150, while the RV shop wanted $300. Before I came in, he told me to make sure I weighted the RV as I normally would drive it, including if I normally filled fresh water or not.