There is a guild on my server was that just created yesterday and is already listed as one of the top progressed guild on the server. I seriously doubt they completed ALL the raids the 1st day they were together. How can this information be verified. I have no doubt that all their members have accomplished these achievements in previous guilds but can not imagine they completed them all again on their first day as a new guild.
Or are they allowed to have the guild achievement simply by having members in their guild who have earned the achievement at some point? I'm confused on that point.