I made a clear edit once someone found the possible dupe explaining why it is not. The linked photo that prompted the question does show a clean Falcon 9, and a perfect explanation was given. Further, the duplicate does not ask about washing, only painting.
I'd also argue the newer question presents the problem better, and the answers are more thorough. Given that, I'd recommend reopening, and then closing the older question as dupe of the newer per the consensus on the main Meta:
If the new question is a better question or has better answers, then vote to close the old one as a duplicate of the new one.
Should I vote to close a duplicate question, even though it's much newer, and has more up to date answers?
Regardless of a second closure/merging, the newer one is not a duplicate of the older one IMO, which I explained in an edit to the question, and is apparent from the answers.