The MOL actually announced the amendment on Dec 9, with more detail: mol.gov.tw/announcement/2099/24259/
The Dec 25 announcement doesn’t seem to have anything new. There was also a similar Dec 15 announcement with one sentence addressing the complaints by labor groups: “部分勞工團體提出「維持國定假日19日」之訴求，勞動部表示，勞工團體的訴求內容可以理解，但對於以闖入及破壞公物為訴求之手段，深表遺憾。” mol.gov.tw/announcement/2099/24303/ It makes it sound like an activist broke a window or something, but maybe they were just waxing poetic about the evilness of activism.
TSMC will observe all 19 holidays in 2016 anyway, to promote health and work-life balance: nownews.com/n/2015/12/09/1914878