I believe this was directed at people running unlicensed auto shops
out of their homes.Of course,all it takes is an overexcited government "official"
for things to get out of hand - or a neighbor who doesn't like cars.
When I lived in California,I had 13 cars,& a two car garage.We lived in
Humboldt County.As long as the cars were on private property,& off the street,
they wouldn't do anything.
Here in Virginia,they can cite you for having a car with expired plates in
your driveway,off of the street.I don't believe they enforce this unless they get
a complaint,or you have multiple junk vehicles on your property.