All of a sudden, people have the ability to determine if distant ancestors came from a different continent. Even if it's just 1 or 2% or even a trace amount, they're checking off boxes identifying themselves as multiracial.
For the 2020 census, it resulted in a 276% increase in the number of people self-identifying with more than one racial group. This is far more than could be explained by immigration or children born to parents from different backgrounds since 2010.
This NPR article (https://www.npr.org/2021/08/28/1030139666/2020-census-result...) explains the dynamic:
Its findings suggest adults 50 and up are most likely to self-identify as multiracial on surveys after receiving a report about the potential roots of their family tree based on a DNA analysis of their saliva. The study of more than 100,000 adults registered as potential bone marrow donors in the U.S. also found that DNA test takers were especially likely to identify with three or more racial groups. ...
"Native American was the one identity people really wanted to have and really wanted to prove," Roth says, adding that she has also found that some people stopped claiming Native American identity after the results of a test did not show any genetic ancestry.
You can imagine the problem when self-reported racial identities could really cloud the waters for determining a suitable bone marrow donor or other health application.