Your opine is incorrect. Facts matter. From the text that you quoted:
Peak ankle plantarflexion angle (regular: p = 0.012, ƞp2 = 0.071, fast: p < 0.001, ƞp2 = 0.137) and peak hip extension angle during fast walking (p = 0.007, ƞp2 = 0.083) were smaller in AA. Equivalency in gait measures between racial groups should not be assumed.
Further:
"In many cases, statistically significant racial differences were associated with effect sizes with medium and large strength showing that these differences hold both statistical and clinical significance...
The continued assumption that racial differences in gait mechanics do not exist causes important distinctions between patients of different racial groups to be overlooked and, as a result, limits the efficacy of the care delivered to patients belonging to racial minorities. The observation of racial differences in the current study reinforces the importance of including diverse and representative sample populations in studies to ensure that results are broadly representative and equitably beneficial across racial groups. Not only are more diverse samples necessary, but clinical consideration of a patient’s racial identity when interpreting and applying biomechanical findings may be important....
5. Conclusions Racial differences were observed in self-selected walking speed and in gait mechanics. The assumption that gait mechanics are the same between racial groups is not valid. Gait mechanics outcomes can be useful for the development of effective medical interventions, optimizing rehabilitation, and determining effective and necessary preventative care. By intentionally studying diverse participants and tracking differences between groups, we can benchmark these differences and use them in the development of future research and individualized treatment protocols."
This study is not proof that you can determine race by gait. That's not what they're testing and they have no position on that. The scientists involved in this study are not racist. They are attempting to make future biomechanical studies equitable with potential implications for therapies. They are well aware of race as a social construct, are aware of confounds, and limitations of their approach. I think they're smart, well intentioned, and I admire them.
THM: Science of racial differences is not necessarily bad, shouldn't be assumed as quickly as a knee-jerk reflex, and also shouldn't be misintepreted.