Chill your tits mate, you could go full AP Riven jg and still win matches up to low Diamond. If the lad liked building botrk on Lee, let him, it's his playstyle. Efficiency has literally no business in such low rated games, as players CONSTANTLY make far, far bigger mistakes (be it mechanical or based on decisions) that overshadow a few percent more damage here and there due to one item.
The only time you'll EVER need an optimal build for every situation is when you get into games where the difference between you and the enemy is in who makes the right decisions both around the map and in the build.