I’m sorry to be so blunt, but this is pure hogwash!
You incorrectly stated “Google had declared that the Sandbox filter is a reality.” When did they make this statement? I have never heard of anyone from Google making such a claim. I believe this statement to be false both in its premise as well as it specifics.
Google engineer Matt Cutts has flat out stated that the mythical sandbox does not exist. So I guess you have to include Google engineers in you list of “skeptics”.
The notion of filters seems to be misapplied in your post. Google’s algorithm uses some filters, but not in the manner you seem to be asserting. Google uses an objectionable content filter that filters certain types of content that may be inappropriate for a general audience and they use a duplicate content filter to help provide diversity in the results, but not much beyond that.
The primary SERP algorithm uses a system of scoring relevance, not filters. When I hear someone use a phrase like “Google uses a system of filters” in a fashion that implies that their algorithm is primarily made up of filters, it makes me chuckle a little. A filter is just that, it filters or removes listings from a SERP. A filter cannot be used to rank a webpage, only to ignore a webpage, as such they are only useful as a tool to totally exclude, not rank or sort listings.
Yes Google uses filters, but only after they have calculated, ranked and sorted the query results and only to exclude inappropriate listings from the final results. They also use some filters, like the duplicate content filter, to prevent their crawlers from spending too much time crawling duplicate content, but that has nothing to do with the SERP algorithm.
I will acknowledge that some folks imagine their websites are trapped in a “sandbox”. This is an imaginary construct that really exists, but only within their minds as part of their thought process. It’s not something that exists in the real physical world. I don’t think it is useful to an SEO expert to use such an imaginary construct. It’s the kind of thing that leads to people believing in dragons and unicorns. They make good entertainment for storytelling in books and movies but you shouldn’t expect to encounter them in real life if you have maintained a grasp on your sanity.