I believe that's the rate for people who seek out a paternity test, which is to say are already suspicious. The overall population nonpaternity rate is about 3%[1].

As an aside, obstetricians often notice nonpaternity because of the child having an impossible blood type for the putative father. The ones I've spoken to prefer to stay silent when they notice it.

[1] https://pubmed.ncbi.nlm.nih.gov/19320216/