For the most part, the contract would also say what the publishers can and, more importantly, cannot do. And while PD is still technically a separate entity to SONY (despite being owned by them) and a developer (though a first party one) and not a publisher, they'll also pick up their own share of GT5 sales, similar to Infinity Ward and Activision, or Bungie and MS. Financially they'll have enough power as a studio on their own to tell SONY to sod off, like, for example, Blizzard (hopefully) kicking Kottick and any Activision guys off the premises.
Maybe it could just be the unique circumstances between PD and SONY. Perhaps neither of them want to annoy each other too much, like a passive-agressive drunk marriage. SONY doesn't want PD too angry because then they'd stop making 10,000,000 unit games, but they want them to change some things. PD doesn't want SONY too annoyed, because they'd get dirt cheap dev kits and the most patient executive producer on the planet (something they wouldn't get elsewhere).
Guess I'm just annoyed that certain parts (interface, mostly) seem rushed and there's no Moon over the Castle opening