Probably the lack of similar structures in the area at the time makes this significant. If large arranged stones from 10,000 years ago were common around the great lakes then we'd assume everyone knew how to move large rocks back then.
This assumes we've been comprehensive in unearthing ancient structures that were buried under water and dirt 10K years ago. We mostly find these types of sites when doing new construction. There is likely countless underground ancient structures undiscovered off the coastline, since sea levels rose more than 120 meters at the end of the last glacial period.
Also, I wouldn't assume at all that knowledge would transfer outside of a localized area. It didn't happen like that in the so-called hearths of civilization like Babylon, Egypt, China, etc.
