Without the italicized reminder text following in parentheses, it may not be clear that this a triggered keyword ability that stacks, while static abilities like flying, trample, and vigilance do not
But neither is required for the decks to work
I have to imagine that there will be a self mill engine printed in Zendikar Rising, so maybe Drowned Secrets will not be missed so much, but I have had a lot of fun playing with it and employing both strategies even if neither one was particularly competitive
It turns out that Mono-Black Commanders are really good at being mean to your opponents, but sometimes we all want to be the villain, don't we?
White already has good removal for handling the big stuff, it is dealing with the little things that white is most eager to expand on and Oppressive Rays gets that job done well
Consistent speed is the most important consequence of all these factors