First time I've seen this; I've always used the Firefox-provided page.
I was initially struggling to see the point of this new effect.
Well, I can see what they're trying to do - focus the user on the primary search area - but nearly all users are going to move the mouse pointer at some point anyway, thus revealing all the links.
Because of this, it's a near-certainty that a user will see those links anyway, so why risk detrimentally affecting the user experience with a slightly longer download time for the effect's code?
And then it occurred to me: mobile devices.
Very limited screen real estate, and no mouse pointer. That's why they've done this.
But yes: for desktop use, it's utterly pointless.