I’ve never heard of racial stacking in any sport. Coaches recruit and play players at their best possible position.
coaches racially segregate athletes by playing position.
Typically players at the same position have meetings, drills, etc.
I guess the wide receivers should work out with the defensive linemen. Maybe put the kickers and punters in with the defensive backs.
For that matter, the lower ranking assistant coaches are in charge of the players at one position. Maybe do it alphabetically instead.