In SR4, Masking only applied to your own aura, and Extending Masking extended it to actively sustained spells, quickened spells and active foci.
In SR5, they've extended the base Masking to Active Foci, with no mention of Sustained spells or Quickened spells. Seems kind of weird if they bring back Extended Masking just for those two, instead of moving the full effect of Extended to the base metamagic.