I believe this is correct. As I recall, exactly zero national insurers operated in the state prior to deregulation, which began in 2007. The regulation was really extraordinarily strict. Pricing was fully specified by the state, including the points model for moving violations etc. Discounts could be offered to affinity groups, but only to the extent that they were actually profitable.

Here's a 2009 AG report on deregulation: https://www.mass.gov/doc/autoinsuranceexecsummarypdf/download