I’m not sure what bit you mean, I have the classic 8 hole boots and the shape is the same from my perspective?
There are differences as i went Matte finish for the Solovairs and obviously the stiching is a different colour (smooth sided sole too) but i’m more concerned about the quality/fit/longevity of my boots than the Docs aethetic anyway.
Having worn Doc Martens most of my life i’ve now switched to Solivair, last pair of ‘Docs’ i bought wore through the upper in 6 months and ripped my feet to shreds, the Solovair i replaced them with are still like new after a year and are the comfiest boots i’ve ever worn.
The only downside is explaining why you’re wearing ‘knock off Docs’ to hipsters, but i generally go with ‘They’re Doc Martens with all the Vietnamese Child Labour taken out (allegedly)’
Yeah, the iconic yellow stitching on Docs is likely trademarked, Solovairs are grey stitching.