^I think what they mean is that Troughton's Doctor set the pattern for the rest in a way Hartnell didn't. In the Hartnell era, the companions were more the lead characters and the Doctor was more of a mentor/advisor. But from Troughton onward, the Doctor was undeniably the star of the show and his companions were there to follow his lead.
I don't think that's what they mean, they're talking about the character of the Doctor more than the format of the show. But, I agree with your assessment along those lines.