Kinda looks like they just sped up the boot-up animation? There's a dark "swipe" or something on the logo for both that goes by much faster on the new boot-up than the old one, so it seems like maybe some frames were cut out from the old one, frame timings were sped up.
It's still a good thing, anything to cut down on load times is great. And it's pretty clever for them to accomplish it by cutting down frame time in the animation. I don't think the change involves anything to do with the SSD though or any bandwidth being boosted. Otherwise the animation speed for the opening sequence would've stayed the same but the new one would initiate much earlier and load to the dashboard quicker even with the same animation timing as the old bootup.
EDIT: Should probably clarify what I mean. So what they seemingly did here was adjust the frame delay timing. The actual number of frames might be the same as the old boot-up because if you slowed down the new one you'd get 1:1 frames most likely.
But if you've done GIF or video editing in stuff like Photoshop, GIMP, etc. and considering what boot-up sequences usually are (simple video files in some proprietary format or a sequence of images animated by some program code with audio timed to it), you'll know what it is.
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