Could be. Below are photos of an original Mk III resized to the same height or length as the new gun and finally with the trigger guards sized the same and aligned.
Based on the photos, particularly sizing and aligning the trigger guards:
(1) the dust cover is longer and the frame and slide above the trigger are taller to accommodate the change in guide rod and recoil spring, take-down lever, and SIG-style lockup.
(2) the grip is longer to accommodate the 17-round magazine.
I strongly believe the frame is longer. Springfield has already pushed the original frame/magazine size to 15 rounds and would have gone to 17 if it had been possible. The only ways to get two more rounds in the magazine are more length (a longer grip or extended magazine) or more width (a wider grip frame).
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I think the original pic is distorted causing the blued version to look shorter than it is.