Kristina, it is a good point, but the G2G is somewhat of a summary of the entire project coverage, which does include a number of other things, including the focus of the Notables project, the concept behind essentially what is a Wikipedia project, the foundation of why Wikipedia is utilized as an independent Notables standard, the way the rule is applied, the methodology of how we apply it to the profiles, the technical steps used to do so, and so on and so forth. To include all that information here in a small blurb above would quickly lose the majority of those who simply want to find a monthly G2G. Perhaps we should review the wording to indicate that this information is only a snippet of the whole project and to read the project page if there are questions, and while it is certainly implied above, it may not be as clear as we could get it. The team will take a look at it and see what we can come up with.
But to answer your question, we use the Wikipedia standard for Notability. Wikipedia acknowledges that formal and nationally accepted National Biographies and National Who's Who (not the cheap fake knock-offs that anyone can "pay" to have their name inserted) are also acknowledged by Wikipedia as either those they want to have profiles for, or are actively working towards. However, as mentioned above, there are always Notables that have slipped through the cracks, who meet or exceed the Wikipedia standards for Notability, and should be considered. Under those circumstances, those individuals would have to demonstrate, typically through a profile on WikiTree or an accepted article on Wikipedia, that they have all the criteria for Notability as laid out by Wikipedia. We usually do that through the creation of the profile, the presentation of it on G2G or to the leadership team, and then discussion on G2G regarding why/why not they meet/do not meet the criteria. Sometimes the missing elements can be fixed. Sometimes they cannot. But we try to openly discuss it so that one person's opinion cannot simply overrule a larger majority group who may think otherwise. However, simply saying "My Grandpa is Notable" and providing no evidence for it will never be sufficient. We have to acknowledge that the intent of WikiTree is that this could be around long after all of us are gone, and we would like the decisions on these profiles to stand the test of time. So we require evidence, at least enough biography to prove their Notability, and enough clear reasoning that someone down the road could look at the profile and say that they too agree it's Notable.
Hope that helps.