It seemed weird to me at the time but I wasn't aware that it was supposed to do that.
Setting the default as non-rotating seems to me to be the best way to go. The reason I say this is because in between rotations it clears the box (table), and displays the "loading" animation, which is fine in and of itself, but I find that because the box shrinks in height when the animation begins and grows in height when it displays the next announcement, the forums listing is jumping up and down on the page. If I scroll down trying to look at all of the forums, I find it very distracting as the list jumps up and down on the page.
I am not trying to knock the mod. It is a great mod and it is what I have wanted for some time now, but I am simply trying to point out what I think might improve it. If it is not auto-rotating, the forum list will not jump up and down.