Original upgrade model 'was not appropriate'
Evolution Studios detailed the PS Plus version of Driveclub and the offer sounded good. Mostly. With a membership, you can play every game mode, 11 tracks, 10 cars, and one location at no extra cost. Then, if you like the game, you can upgrade to the full Driveclub experience for $49.99. Cool. Not cool was that should your PS Plus subscription ever lapse, you'd be locked out of that paid content. You don't need me to tell you why that's a bad plan.
In reporting about the upgrade originally, I had figured there was some sort of miscommunication in the announcement post. But, no, the video about Driveclub also mentioned the PS Plus requirement. Thankfully, Evolution and/or Sony have been receptive to feedback.
"Now, if you intend on downloading Driveclub PlayStation Plus Edition, and upgrading to the full game experience, you will have access to the full game even if your PlayStation Plus subscription runs out," reads an update. "PlayStation recognizes that the prior plan ... was not appropriate."
DRIVECLUB PlayStation Plus Edition Details (Updated) [PlayStation Blog]