From all the lore we have the Edicts were two things:
1) An active banishment of the gods
2) A barrier that forcefully kept them out.
The concept of an alarm system, guardians set to reawaken guthix and guthix erasing the world are all things you have made up. We don't even know if Guthix CAN erase the world since Elder Gods made it and they far exceed him. The Alarm system seen in TWW is an alarm on his resting place, nothing to do with the edicts. Also the idea the Guardians would awaken him seem stretched in that even in the heat of battle in TWW they were doing everything they could to STOP him being woken.
You find me a confirmed source that proves what that article says, then I'll understandable accept that I was wrong. Until then, I have no reason to discredit the article based on my 5+ years of questing and lore interests.
The Edicts were always initially perceived as a barrier - but it's also possible it was a threat. And yes, Guthix could have erased Gielinor. He had the sword and the Stone of Jas at his disposal. That changed when the SoJ was stolen, but it was still available to Guthix when he went to sleep. The Guardians knew where Guthix was resting, and they could wake him up if the situation became so dire that the only option available was for Guthix to return.