Sure, saying "X are too timid" is a stereotype, but pointing out at a diversity seminar that you should be extra observant around X because they tend to not speak up for themselves is just good advice. Many cultures value being quiet and doing your job a lot more than others, and those values get passed down by parents for at least a few generations after immigrating. If that group doesn't have a good support structure (no BLM equivalent), that only adds to the fear of speaking out.

If you're a manager that gets many complaints from group Y but very few from group X, knowing that might lead you to do some more investigating and discover group X is being treated even worse, they're just not reporting it. Using a heuristing to optimise your search given imperfect information, if you will.