I would say it is anti-consumer. Many of the PS+subscribers, most probably, has no clue about this and will think "hey, a cheaper version of the game." It's trickery, and I'm not fond of it.
And for many of those PS+ subscribers it will nothing but that, they will play the game a couple weeks, then stop and never notice that they can't play it anymore when their PS+ runs out. Also I'm sure this piece of information will be on the PS store page of the PS+ upgrade, so people can just read up on it without extensive research before making the purchases
Most people pick their games up again from time to time.
And you put too much faith in the consumers. They don't read.
I'm aware people don't read T&C, but Spending $50 without even reading the first line of the information on the right hand side, that's in plain view, is just negligent.