Have you ever seen limestone of any kind weathered by water, salt exfoliation, or any other type of weathering? If you have, then you'd know that they do leave evidence. If you've been in a limestone cave, you'd realize that in most cases the cave is specific evidence of weathering.
I'm not going to do the url thing but you need to take a look through these pics. Unfortunately for me, I'm on my sister's laptop which has some security features in which limit me from pulling up the pics easily for you, but the links work just as well. They all show various limestones throughout the world that show various types of weathering. I've also included some articles regarding the various weathering of Egyptian monuments as well.
[www.iiconservation.org] (scroll halfway down---Investigation into Environmentally Driven...)
El-Merdani Mosque in Cairo
Limestone dealing with the Amarna period (specific the type of stone and the weatherng seen and mentioned)
Preserving the old Necropolis
Here is the link regarding limestone weathering of monuments in Cairo. The pics are clickable and will enlarge to show you more.
Differential weathering or preferential erosion - Selective weathering which involves the loss of less consolidated material exposing the most resistant fragments. (This is from a basic geology textbook)
Eolian Processes and Arid Lands
More things dealing with weathering, and some references
Conservation information regarding limestone and salt exfoliation
I don't know if I read your post wrong, but each weathering process does have a look/pattern to it. This is shown by the pictures in various links I've given and also if you've ever done conservation work on any outdoor monument or statue, you'd see it, especially in high pollution, high moisture areas.
Like I pointed out before, I'm waiting for Mr. West to clarify his latter statement as it doesn't seem to mesh with his earlier comment. With the inclusion of the articles regarding limestone monuments in Cairo, I'm curious considering many of them are from similar limestone from nearby. Further, with the Sphinx having been exposed from the tip of the head to its tail, it has been exposed to wind erosion, air pollution, salt exfoliation, chemical erosion (carbonate liquid), etc, we have other newer weathering marks as well. I'm curious how it's possible to say all of the Sphinx has salt exfoliation (even if it's in minority, weathering wise according to him) but yet it be everywhere but in that particular area. The only way I can think it's possible is if that portion of the Sphinx isn't made from limestone, but some other stone material. I'm hoping he'll clarify that for me so I can understand his point of view, though I may or may not agree with it.