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> wracking my brain on the logistics of that (more below in the Odds and Ends).

Celestia said Rainbow Dash's and Applejack's antics meant that the leaves didn't fall and that they had to run again.

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How? How did two ponies contribution matter enough that a significant percentage of leaves didn't fall? It doesn't make sense! Then, just them rerunning the course was enough to complete the task. Maybe I could reach on a limb and say disharmony vs friendship magic was at play here or that the element bearers magic is stronger and matters more though there is no suggestions for any of this.  Like, other things I can come up with elaborate theories with both fun and sometimes seriousness that just "smooth things over" but here I got nothing but cute magical horse show. For me though, that is an mostly alright answer. I remember a lot of fics early on tried to down play/rationalize these elements to the point that it feels disconnected from the sincerity of its whimsical nature. 

Twilight Sparkle being slightly athletic:
This is a trait that I've seen be argued was forgotten in latter seasons. This is a position I partly hold but I think I will have to rewatch more of FiM in general before I fully agree with that assessment. It is not as pronounced as her snarky attitude and I could see this being one of the things that is more incoherent. 

Inches...
Pinkie said "Applejack is inches ahead." Very minor note. I have always liked the idea of some sort of ponified measurement system using things like, hooves or wings, over just the implicit US customary system. Not saying inches violates this, just noting.