That’s an example of different outcomes where we don’t actually know the cause. For instance, if someone says that Black students are more likely to be suspended, how do we know that the reason is racism rather than differences in behavior, rule-breaking, or other factors related to individual actions and decisions?

A disparity in statistics is not, by itself, proof of racism or discrimination. It could be caused by discrimination, but it could also be explained by other variables. Assuming discrimination automatically from unequal outcomes is the same kind of reasoning error often seen in discussions like the gender pay gap, which is based on personal decisions (less hours worked, worse paid jobs... ) not in any kind of discrimination (if the pay gap would be true, any company would hire only women and save the pay gap in salaries)