Top lane scenario
Darius runs into minions trying to all in lvl 2 gets ignited so q doesnt really heal much and he's sent home early for fb. Teemo has to back because hes very low and doesnt know where the enemy jg is. Darius teleports back with having bought nothing but has a lvl advantage and is up 8 cs after Teemo gets back with boots and a long sword and enemy minions are dying to teemo's turret. Does Teemo really have the advantage after the fb?
(IRL I called my jungle to force him to back after i got back to lane so his exp/cs advantage was negated, but let's say if there was no jungle involvement how does this play out...?)