Good to see you GJ!!!
Unfortunately, this is nothing new.
Google does it themself.
They wanted to treat subdomains as separate sites, they got what they asked for. Mirrors of entire sites on subdomains they either cannot or do not want to filter/remove from the index.
Whether or not a site is useful makes no difference to me. One "version" of it in either a folder or on a subdomain is useful. Two or more versions is SPAM.
Dave