I do acknowledge that Petra might follow a strategy of scorched earth, but it does not win anything itself (destroying own buildings does not bring back any resources, I just learnt - it couls be a strategy in an emergency situtation where e.g. wood is missing to build new troops). I do see the advantage of not offering further advantage/buildings to the opponenet though (classical scorched earth). Shoudl we add that to the manual or the tips&tricks somewhere?
As a bottom line, the benefit as an attacker is to either destroy enemy buildings yourself, thus getting a loot, or conquering them before taking over the CC then you benefit from additional buildings.