Grape Juice

Question

I have recently hears that Sepharadim cannot bake a beracha of Boreh Peri HaGeffen on American Grape Juice and most of the sweet wines. I was told that because they are made from concentrate, they have too high of a water concentration and the proper beracha is Shehakol. Is there anything to this, or does the Beracha follow the taam?