"Testing"....
The technical skinny on the 4gb exe patch, is that it is an entry in the .exe file's header, essentially turning on a feature that is handled by the operating system. There is no "testing" that needs to be done. It is either on, or off, that's it.
Now, if they are enabling systems within the executable to take advantage (aggressively) of the additional memory, that's entirely different. But I haven't seen or read anything to this effect on it. Who knows with Bethesda, they will often sneak in changes without mentioning them to a soul.
I've found most gaming companies release vague update descriptions, for whatever reasons, I'm sure you could come up with a few of them. The steam platform updates are the only ones I've ever seen that sometimes go into almost hilarious detail or rage with the use of parentheses as to what exactly they fixed.
- Fixed steam://openurl and steam://openurl_external links opening black pages in the existing window in the in-client browser at times (really!)
- Made the screenshot manager prioritize loading screenshots that are visible rather than just loading them from newest to oldest (so you see what you've just scrolled to if you scroll around while loading)
lol.