The hole in your logic is it applies to the carpet, and still ignores my point. The only logical argument in regard of the opening comment you could have made, someone already made for you:

"... most of the times a flight spell is extremely mana-hungry, and he's about to fight an enemy that's actually stronger than him, going with empty mana reserves would be a bad move"

Wanting to conserve strength at least serves some logic. You, however, fired back as if different objects going at different speeds would be a factor between MC flying and MC using the carpet. Memory erodes as obviously I haven't touched this book in months, but the mechanics to my memory for flight in this story aren't broken down. But if a carpet can be counted on to expedite the trip from point A to point B, then so obviously could a caster doing it all his own. Given no reason to believe carpet is different from caster, there's no reason to assume magic flight of a carpet will be different from magic flight of a caster, aside of MP consumption.

That his targets started out way before him is irrelevant. It's still just a stall technique for the writer to stretch out the saga another chapter or two. If I have to rescind anything, it's attempting to follow your silly argument over speed to begin with.