WCG Dota 2 Rules – Backdooring

Heyya guys, I saw and read the Dota 2 Rules for their upcoming campaign (WCG 2019 Xi'an) but there's 1 rule that is too much obvious to me and I need an explanation. The rule is "Backdooring is allowed"

I think backdooring is allowed but the regeneration and armor buff of the tower is the punishment. Ever since 2012 when I first watch DotA 2 tournament, I haven't seen a tournament that doesn't allow backdoor (If there's any, reply to this thread)

Way back in Dota 1 Backdoor is illegal, but Dota 2 is more polished today (except if they have custom rules) I remember bulldog hide a creeps in enemy base to disable the backdoor protection.