Great Google Exodus of 2017
everipedia.org
everipedia.org
and
https://productforums.google.com/d/topic/websearch/25FKBqgHd...
More likely it's the case that people (non-Google people) curating multimedia of black American inventors are more likely to include metadata tags within the multimedia than other curators of inventors, and that Google weighs metadata tags much more strongly than other context. "American inventor" is a solid hit for an image tagged as "Black American inventor". A tag of "Black American inventor" is even a solid hit for searching "White American inventor". I'm regularly annoyed by the way Google ranks hits lacking one of my keywords higher than hits that include all my keywords--I choose my keywords very carefully, damnit!
Just a single website doing this could theoretically throw things off if the material was high-quality, and especially for those more highly structured filters that attempt to dynamically generate ontologies. Biases like this which happen to favor or exaggerate normative expectations are going to go unnoticed. Nobody on the alt-right is carefully cataloging search terms that only show white historical figures to the unfair exclusion of non-white figures. Classic confirmation bias.
Do you really think Google has people coding in diversity rules into their low-level search and query code? "Diversity" is already an incredibly nebulous term, and the unintended consequences of excluding meaningful and relevant data obvious. Just from either a pure engineering or business standpoint this would be stupid, no matter Google's political bent.
I could plausibly see them doing something like, say, one-off, pre-generated results for very specific queries during Black History Month. But as you can see from the above posts and elsewhere, people are making much broader claims and using many more supposed examples.