Why is it called the "mandatory fifteen overs"?

Yes. Why?

Whatever the reason is, its stupid because they are not.

It kind of feels like getting your pocket picked. This has never happened to me, but if I were to imagine what it would feel like, it might feel like this. Test cricket calls for devotion from its fans. You have to watch the damn thing over five days and some of it is Chanderpaul batting. Thats a lot of your time invested. And then the players are just allowed to walk off with an hour to spare, either for tactical reasons or because they simply don't feel like it. It is plain wrong.

It isn't about whether Sammy or Dhoni made the right decisions, its that they should not have the capacity to make those decisions. It is a terrible rule, because the injustices that it sometimes causes are so much worse than the little periods of dreariness it seeks to avoid. In Zaltman's words it is a "nonsensical insult to Test cricket's supporters".

The other rule that is manifestly unjust to followers of the game is the limit on how long play can go on when there is sufficient light. When the required number of overs have not been bowled in a match, it is a travesty to watch players troop off in bright sunshine simply because "it is six o clock".

Is it too much to expect of the ICC's cricket committee to suggest corrections to these glaring instances of bad rule-making, instead of unleashing their powers of imagination on when power-plays can be held in ODIs?

These are bad rules. Change them.