I don't like the added organ and car keys, Carl's voice with not enough grief in it...
The car keys AWS part of the original arrangement - listen to the sessions. And BW's music, to my ears, has never needed an expressive voice to put across the intended emotion, which is actually expressed by the melody and the arrangement, and of course the production.
Carl nailed that vocal. Immaculate.
You are right, the car keys were in the 1967 recording. I even remember having read years ago about the original session that Brian at one time says about the car key player (hee hee): "Now THAT sounds like jewelry!" Recently I read the Badham book, where it says on page 293 about the 1971 sessions: "Two organ overdubs are made, along with Brian's car keys providing percussion." So I thought they were all 1971. But anyway, the point is the keys are really loud in the 1971 mix, too loud for my liking, no matter if additional car keys were recorded of if they're all from 1967. They're not THAT loud in the track only version on the 1993 GV box set and hardly audible at all in the famous Anne Wallace version.
What you and me have written about Carl's vocal is of course both totally subjective, so I can't argue with that. I think he sang too sweetly. IMHO expressive singing adds to the quality of the arrangement.
Talking about subjectivity, I think the 1967 version of Surf's Up is played too fast... And subsequently, the 1971 version too.