United Kingdom

That number is very odd given the high hit rate with most searches.
Maybe the police genetic genealogists are not well trained.

I myself have done these searches for quite some time for adoptees looking for their bio parents.

Yes Gedmatch is used by law enforcement.
It is quite possible to get enough information from Gedmatch to narrow down suspects from that site.
And there are some workarounds.

Keep in mind the criminal is not the one signing up for site, but relatives who may not even
know there is a criminal in the family.

I think it quite irresponsible of the police to not track down the person who is dumping babies.
Three babies are very lucky to be found alive. Those coming down the pike might not be so lucky.