I don't think this has anything to do with simplification. People who offer defenses of that definition of "racism" never seem to bring up simplification as a benefit.

I suspect that it may have more to do with intentional control of the discourse, wielding language as a tool of power to achieve what they believe is a noble end. "Racist" is a supremely powerful charge. What if you could gain exclusive use of that word as a weapon to use against the agents of injustice?

The reason that I suspect this is that there is significant overlap between the crowd for whom "racism" means "racial prejudice backed by power" where "power" conveniently means "exactly the amount and nature of power that white people have and have had over minorities", and the crowd who is partial to critical discourse analysis. Critical Discourse Analysis is "a qualitative analytical approach for critically describing, interpreting, and explaining the ways in which discourses construct, maintain, and legitimize social inequalities". Hmmmm. You'd never imagine that someone who studies CDA would try to craft discourse in a way that would construct the kind of social change they're seeking, would you?

And if we look up who DiAngelo is, Wikipedia tells us: "Robin Jeanne DiAngelo (née Taylor; born September 8, 1956)[1] is an American author working in the fields of critical discourse analysis and whiteness studies."

So to believe it's really just an "innocent" (elitist) simplification, I'd have to see some very good evidence, as the alternative hypothesis of intent has enough circumstantial evidence behind it to be taken seriously. Otherwise, I would tend to defer judgment pending better evidence.