When going for a Zone 2 run, if another runner overtakes you, your Zone 2 run has *not* magically ended.

Yes, because you’re the one surprising them in all black, not the other way around.

“It’s not that serious.”
Too many instagram running influencers with their running vests, hydration packs, and fancy cereals, energy gels, etc - all for a 10KM run (<6 miles) and the crazy ‘chasing the chickens’ or whatever its called, warm up routines.

This is excessive. OK maybe water if its really hot outside - beyond that though, being properly hydrated in general and having a drink when you return will do.

I thought stretching was scientifically ambigious, with just as many studies saying it hinders performance as it improves it?

I’ve never done it myself, I do warm up - but actively, with either light weight (weight training) or low intensity warm up jog (when doing cardio, even before a time trial or vo2 max protocol).