Sprint has been doing this lately, saying that you are able to upgrade. But when you look at all the info, all they're really saying is that if you pay off your old phone, you can upgrade. Has nothing to do with the Galaxy Forever plan except that you can upgrade after 12 payments, whether you take 12 months, or 3 months, they'll still need 12 payments before upgrade, plus your old phone.
Not just lately, they have a rep for doing shady things. Had them a few years back, it was a horrible experience all around. And while all carriers have they sketchy practices, Sprint seems to have quite a few more....