That is entirely possible, however...
Horsepower rating is a mysterious thing when it comes to Briggs, you'll find the same CID often covers a broad range of horsepower ratings. dependent upon specs supplied by the company building the mower. For instance the 28 CID Flathead has been rated for everything from 8hp up to 15hp. The 44 CID Intek V-Twin, is rated from 20hp up to 26hp. And, that is the reason many devout racers and engine builders refer to these engines by CID rather than horsepower.
What changes are made to effect the change in horseopower rating... carb adjustments generally, slight changes in timing, and on very rare occasion a little different cam. Otherwise they're all the same. It wouldn't surpise me in the least to see the 42 rated 14hp - 18hp honestly.