Is that why The National Review feared that he was another David Souter?
The National Review might have had some misgivings, given the strong pull of identity politics in this country, especially for a member of a minority like Thomas. That doesn't mean, however, that they considered him a "blank slate."
Thomas was well-known even in his EEOC days as an Ayn Rand libertarian. He used to have his staff view The Fountainhead during lunch hour. He also had a name of his own around DC, unlike Miers, who no one had ever heard of!
An honest read of this post -- Post #139 --- on another thread should convince you that your comparison between him and Miers is way off base.