I understand what you're saying that One Piece is an object/treasure, but the story of said object is not only its revelation and secrets, but also its consequences, repercussion and debate. The whole manga is about the One Piece since page 1 from chapter 1, and all of the series' trajectory and ending is also the "story of what One Piece is". The final war that will engulf the world is part of that same story since they're connected, so there's no need to separate one from another.
It is contrived since this is such an ambiguous distinction that is completely unnecessary as an answer, especially when you think about the context that originated this question for the SBS. It implies that all of Oda's previous comments about OP ending in 5 years (which were very straighforward) were also secretly layering this sophisticated distinction without ever mentioning it, and that Oda was never actually saying that OP would end in 5 years.
Of course, you're saying that this happened because Oda is backpedaling from his previous comments, and that's also why it sounds so weird, since Oda is finding a loophole to do this backpedaling. That's a possibility, but I don't think it's very likely.
Btw, Greg just said that the Arashi interview happened after volume 97 was submitted for printing, so if Oda was already backpedalling when he answered the SBS, then he wouldn't have said that OP would end in 4 or 5 years in the interview.