sir, just to clarify. Naging bawal lang yung backdoor dahil dati, kahit hindi pa nasisira yung outer towers, pwede na i-attack yung throne. So yung mga abusive Furion players nagteteleport sa loob ng base ng kalaban tapos sisirain yung base. So players implemented the no-backdoor rule that time. In modern DotA, towers and structures are invulnerable if the outermost towers aren't destroyed yet, so obsolete na yung strategy na yun. You are allowed to attack the outermost towers anytime, if this was unintended, they would have made them invulnerable also. This is a legitimate strategy, and there is already a corresponding mechanism to make this harder(towers have higher armor and HP regen if it is being attacked without creeps near it).
Of course sa pustahan, kahit anong conditions naman, pwede niyo i-set.