As the genetic sequencing graph grows, the odds of maintaining anonymity rapidly drops to zero. Poor choice of words on parent’s part, but I think one can understand what they were trying to convey (datamining the genotype matrix).
Disclaimer: Interviewed at 23andme a decade ago. Good folks.
I think that commenter was thinking that 23andme would be able to identify many people as children of the same unknown person, but unless that person also submitted their DNA to the service, they would effectively be anonymous. An unknown parent of dozens or hundreds.
They’d only be anonymous if none of their family had used 23andme. CODIS already supports similar familial searches.