Thoughts.....
I think you are probably right, All the clues point in that direction don't they. However I would want to be taking the top belt cover off and verifying it by eye before I'd be truly happy.Yes that's been done. 100%. The mark on the top of the cover is what the mechanics mark to show it's been done. The sticker peeling off is also a big give away as the cam cover bolt is under it and it has to be peeled back or punctured to undo.
100% it's been done.
Apart from wear, whats a tail tail sign its been changed?