Impressive from a drill-and-ceremonies perspective.
I wonder if they're ceremonial units or regular units?
Ceremonial units would be like at the Tomb of the Unknown Soldier, Arlington National Cemetery, Buckingham Palace, etc.
Usually only the best Soldiers get selected and assigned to ceremonial units.
If a regular unit spent as much time as it would take to get this right, their deployment training and readiness would suffer, so likely ceremonial units or Soldiers detached from their regular units for periods of time.
OTOH, such symmetry and sync might be an essential skill for the march west (road movement with millions of Soldiers marching and avoiding trampling and domino effect)