The 5.3 fps velocity change is small in absolute terms but critical in precision: entry corridor margins at lunar-return velocities are measured in fractions of a degree. A corridor too steep risks excessive g-loading; too shallow risks skipping off the atmosphere.
With RTC-2 locked, the trajectory is functionally final unless RTC-3 is commanded. Orion began its return from the lunar sphere of influence and NASA fired an earlier correction burn to set the baseline; RTC-2 closes that sequence.
