This is utterly rubish. If the state wants to know who is homeschooling they can look at the PFD records minus enrollment data in the ANSWERS data base held by ACPE. Before ANSWERS, they could use borough level recreation records, so let's knock offthe " we don't know" struff, because they DO know. The issue here is not how many. The real issue here is that OCS  is looking for ANY reason to come and invade homes.
These folks receive no money from the state and thus the state has no legitimate reason to intercede unless there is probably cause that a crime is being or has been committed. The parents are accountable--because if you  mess it up you are stuck with the kids living with you rather than being independent. 
What happened in this case, if true, was terrible, but to suggest all homeschool families are terrible because one is is a bridge too far.