Interesting note: https://x.com/SpaceX/status/1760882381148623202#m
One of the nine Merlin engines powering tonight's first stage is our flight leader, powering its 22nd mission to Earth orbit
I didn't know that the engine flight leader numbers were higher than the booster flight leaders. I wonder how this occurred?
I assumed that they swapped out engines only when they needed refurbishment, and that the engines would always have fewer flights than the boosters. I guess some older engines have been reinstalled in younger boosters?