For example, a german unit stack facing three adjacent soviet unit stacks; Do I really have to attack (as the german player) all these three enemy units?? If yes... gosh! :-D
That's the way I've always played it. And you're correct in your assessment, although I'd say "Wow!"
This is why some claim that this game seems more like WW1 than WW2 -- since you're not able to choose a Schwerpunkt until the Exploitation phase. What this actually means is that you must choose where to manifest your major efforts and place your best units there, leaving other units (weak infantry) to perform what used to be known as "low-odds attacks" or "soak-off attacks." So concentration of force in this game's combat phase is still possible, but often comes with a heavy price tag!
Hope this helps and that you enjoy this nifty little game!