It would be very helpful if user could edit content of cells when PageMode = false. The world is dynamic, you can't expect the user don't want to change things. There are many examples from every-day life that answer the crucial question why? For example the first value entered can be mispelled and the man who works with database want it correct. Try to view on situation from point of view of end user. I see no problem in enabling editing mode when PageMode = false. I accept that new value will not be written to database. Even when this is not ideal I can solve the problem by implementing some event handler.
P.S. I principally don't use PageMode because of many visual errors (for example problematic scrolling with mouse wheel). PageMode is not answer to my problem also because of serious flaws in design that are outside the focus point of this contribution.
You can use editing when PageMode = false, just set goEditing = true in grid.Options but as you mention, it will indeed not be saved back to the DB as the DB connection with the grid is no longer active.
This feature will not be implemented.