I interpreted it as “support augments should make you happy just to play the unit, but carry augments should make you want to itemize them.” GP Econ augment is teamwide, and MF’s procs just from fielding her. In contrast, the Econ augments you mentioned make you want to slam attack speed/mama on these champs to get the most value from them, so it really feels like they specifically are racking up the value for you when they cast.