This is the offending image;
Taken as a whole it doesn't look
that bad I suppose.
lol)
Since the engine is obscenely detailed I guess they've got fairly aggressive scaling on that particular part of the car, because at a glance everything else looks the same detail wise. I also have to agree that the 'distances' in both images is not the same, nor the composition, environment and various other factors such as camera settings which may possibly affect the swapping in and out of the higher detailed engine bay.
Based on GT5p and the demo pods of GT5 (both in-game and replay) I'm not concerned about the level of detail on these cars in or out of photomode. Indeed this could just be an isolated case where the car dictated the methods, we don't know yet.
Is that true? I never noticed any difference except in aliasing?