Nope. I just looked at a 64oz regular grape juice in a plastic bottle and it says it has from concentrate in the ingredients. Its only the glass which does not. Although some plastic bottles say added for taste while others do not. You may be right that there is no added water though and thats only in the light juice
I also just looked at a Kedem plastic 64 oz. It says "
may be sweetened" with GJ concentrate.
What exactly can be the pshat of "may be"? Does it depend on what the mashgiach ate for breakfast that morning? Does it depend on how sweet that batch of grapes came out?
Does that really matter for Arba kosos?
BTW, Reb Moshe paskened that one can only use wine for the arba kosos, not grape juice, FYI.