You're right they seem to be addicted to aren't we clever shock twists and misleads but you're right they just made it easily for people either intentionally or not to misinterpret it. They could have written the scene much more ambiguously and let James in on it. You've got a good actor trust them.I don't doubt that they may have meant for it to be that Spike was meaning he was going to get his soul when he went on that quest but they tried to be too clever with their interpretation and left themselves wide open for others to question their thought process and what played out on screen.
Spike can't be told 'You want to return to your former self, when his former self has/had NEVER been a vampire with a soul before so how could they possible make him that on the end of his quest. They would actually have had to made him a souled human again but of course that was never going to happen because he would not have been as useful for the final battle as a human being.
Make it make ABSOLUTE sense so no one can question the process or the end result.
I believe they shot themselves in the foot with this situation for Spike. Not about him actually getting a soul for Buffy (which I didn't actually agree with in the first place), but complicating it by trying to throw people off of the real reason for Spike wanting to win his quest. I understand they wanted the shock factor when it would be discovered what was happening to Spike at the end of the season finale but that even to this day, that many still question all that occurred and truly believe differently, shows they fail somewhat on what they wanted to achieve.
If they just HADN'T put in THAT line so even when Spike had won, they could have just said 'your request will be granted'. Still could have had the mystery of what had he asked for without there being the slightest perception or any doubt of what was happening to him because of what had been said before.
And then to hear that JM would have played that screen differently if he had really understood what was truly happening to Spike hows that even up to the point that it was revealed he was getting a soul, the way it was presented on screen felt it was a going to be different outcome.
So it kind feels like they mislead JM just because they thought they would blindside their viewers in assuming that they would be convince by what they were being shown.
And that Spike on his quest, rode off on a motorbike?! Isn't he a vampire that still can be harmed by the sun....