fundamental flaw in sandbox theory?

there's no doubt in my mind that some sort of new-site filter exists in google. I've seen it first hand, and read plenty about it as well.

I'm not questioning the existance of the sandbox. what I am questioning, is how a site is determined to be "new"- the common, well-accepted theory seems to be that google simply follows the domain whois. seems like it'd be a logical, normal way to determine the age of a site, right?

somehow I'm guessing this isn't how it's done. most SEOs out there seem to be of the opinion that new pages or folders on an existing site will rise in the ranks more quickly than they would if they were on a fresh domain. subdomains, however, are supposedly treated as a new fully-qualified domain name.

but these two don't mesh: subdomains are going to have the same whois information as that original domain.

what's this mean? either we're flat-out wrong in our assumption that subdomains have been treated as new domains, or google determines how new a site is by something other than simply the domain whois.