I think this is mostly true, and it’s a common mantra across anthropologists and scientists, but it’s worth noting that the idea is misused and frequently touts a modicum of intellectual dishonesty.
It would be more accurate to simply assert that genetic diversity is fluid and limited in scope among human populations. This doesn’t really mean there’s no such thing as race, it just means that race isn’t an absolute concept. There very much is genetic variation based upon historical population ranges among the human family, and it’s clearly observable. An example of this would be the propensity toward sickle-cell anemia seen in historically African populations as a result of increased exposure to malaria driving a biological evolutionary need to minimize risk from the disease.