Do some due diligence on the agc_center vs agc_nominal columns

: I'd love to understand what the first code block (if False) means;  it gives much less scatter than the second.
I think that agc_nominal_x_mm must have absorbed the per-AG motion somehow, but it'd be good to check the code
Untitled
 
    if False:         # RHL misinterpreted the agc_match columns
        agcData["dx"] = agcData.agc_nominal_x_mm - agcData.agc_center_x_mm
        agcData["dy"] = agcData.agc_nominal_y_mm - agcData.agc_center_y_mm
    else:                               # from agc_data and pfs_config_agc
        agcData["dx"] = (agcData.centroid_x_pix - agcData.agc_final_x_pix)*(agcPixelSize*1e-3)  # mm
        agcData["dy"] = (agcData.centroid_y_pix - agcData.agc_final_y_pix)*(agcPixelSize*1e-3)  # mm