Not that anyone would feel such a small difference, but it is still somewhat of a departure from issuing thinner and thinner tablets with each generation. The thin game was getting stale anyway, current phones and tablets are already anorexic enough, so it's high time that a line be drawn, and the focus is moved to something else.
That something else for Apple might be a bezel-less iPad Pro 10.9, which would eventually come to replace the current Pro 9.7, and fit a larger display in the same footprint. That one is allegedly going to be 7.5mm thick, like the original iPad Air, which means it will be thicker than its predecessor. According to insiders, the new iPad Pro 10.9 (previously rumored to have a 10.5" display) has no home button, and is just frame on the sides, with no meaningful bezel width to grip on, save for the top where the FaceTime camera is.
The new iPad Pro 2, on the other hand, is also said to sport bezel-less design on the sides, apart from the top, while Apple's iconic home button might be gone for good there, too, claims the source. Let's not forget that Apple is rumored to employ under-glass home key in the upcoming iPhone 8 as well, so the new iPads, which could be announced in the spring, might be a harbinger of things to come.