I still think you run into a 110.3(B) problem. What do the installation diagrams show?

There is no listing violation if one installs using the back screwholes.

When I look at the SqD site I see two different numbers for surface and flush mount 3r "all in one" panels (just an example). Is the difference only in what cover you get or is there another difference? How are they labeled?

Maybe Jim Pauley can answer that. Anyone talking to him lately?

Can you post the links to what you are looking at?

Flush panel

http://www.schneider-electric.us/product...;countryCode=us

Surface panel

http://www.schneider-electric.us/product...;countryCode=us

Otherwise spec'ed the same.
Is the only difference the cover?
Does it come with different installation instructions?

It may not be an issue but I know a lot of things here have come down to what the manufacturer says in their paperwork.

I do not have a huge problem with these things being flush mounted except for the service entrance conductors traveling any significant distance in the wall, even if it does make a "neater" installation.

When you look at 408.37(A) (panelboards) or 240.32 (enclosures for overcurrent protection), they both specifically refer you to 312.2(A) not 312.3. 312.3 appears to be describing loadcenters that are flush mounted.