Vulnerabilities have lurked for years and even decades in the Windows codebase. I'd not be so certain that having a snapshot today wouldn't help you find exploits for a long time.
Yea, how long was OpenSSL’s heartbleed an issue? And that was open source that was supposed to have millions of eyeballs on it. I agree, I don’t really buy that MS rewriting everything hourly and there is nothing to get from source.