"There was a spillover effect," said Kevin M. Esterling, a UCR professor of political science and public policy and a co-author of the study. "It wasn't just a reduction from the de-platformed users themselves, but it reduced circulation on the platform as a whole."

I believe the term that you're looking for is "chilling" not "spillover" effect. This not a novel effect of censorship by deplatforming.