Plymouth has been big on a 1620-2020 (400 years in America), tourist theme for the year. It’s an important industry for the town. You can believe the locals are going to track this down.
Other than that, no one is really sure if that is the actual rock that was the first one that the settlers stepped on.
If you read about early Mass. history, the Pilgrims first stopped at Provincetown ,realized after many months on barren Cape Cod they had to get to the mainland, and crossed Mass. Bay and landed in Plymouth. - Tom