I'm not sure this is a fair assessment of the change. I don't think it was a simple relabeling; I think the intellectual foundations also shifted.

If you read Bell's early works, when it was called Racial Realism (after Legal Realism, which aspired to be scientific in a something like the positivist sense), you will find a great deal of thoughtful appeal to evidence, plus consideration of the relative importance of different factors. Legal Realism and Critical Legal Studies--the latter based in the nominally science-affirming but methodologically anti-scientific Critical Theory tradition--were competing approaches to modernize the legal tradition.

If you read Bell's later works, it's not--to my eye at least--just the same style of stuff with a new label. It is less evidential, more narrative; more about power, less about principle. To me, it reads like Bell's early insights were recast from one intellectual tradition into another, from being based on Legal Realism which in turn was (I would argue) based on Positivism, to being based on Critical Legal Studies, which in turn was based on Critical Theory.

And later Critical Race Theory scholars proudly display fondness for narrative over studies, and from my reading anyway seem much less inclined to name or consider any factors except those that they want to call attention to. So whether or not the name change was substantive at the time, it was apt.