It would be interesting if there is anyone in this forum who is from a university's institutional research admin. department. It would be nice to hear their comments on why almost every US university does not follow the US Census Bureau's Guidance on the Presentation and Comparison of Race and Hispanic Origin Data.
OP, I think you said you were a sociologist. If so, rather than waste your time here, why not research, write, and publish? I see at least 3 papers.....
1. A qual paper -- notes on...... -- based on some field interviews of IR people, what classification approach they use, and why.
2. A quant paper sampling 100 colleges, say, and testing the use of that Census Bureau typology in publicly disclosed docs.
3. A survey of IR people on reasons why they use the classification approach they do. Quant again, nathc.
BTW, have you talked to IR at your own school yet? That would seem to me to be the place to begin, both to satisfy your own curiosity and as a way to begin on the first paper.