Has the "previous selection" command been smoking something? It seems to have very little short-term memory. About half the time I use the "ctrl + <-" keys to try to restore a previous selection I end up with nothing there. What is up with that? The restore previous selection command needs to sober up and pay better attention! It should work at least as well as Autocad. Yes this is a small item but worthy of a quick fix nonetheless.
Looking at the Revit manual it appears that this lazy behaviour is intentional...
"Restoring Selection
If you have selected an element or multiple elements and clear the selection, you can quickly restore that selection by pressing the left arrow (<—) key on your keyboard or by right-clicking and choosing Select Previous from the context menu. This command is most useful when you have a complex selection that you accidentally cleared.
You can only restore selection only while Modify is active. If you switch to a different command, the selection is cleared."
Why have a rule that clears the previous selection once you change commands?