It's perfectly logical. The 17" sizing standard refers to the diameter of the wheel where the bead meets the rim. This is the critical design dimension and must remain consistent across any wheel design so it can be used for any 17" tire.
The wheels are actually larger in diameter if measured across their face as there's a lip outside of the barrel of the wheel to catch the bead of the tire. The exterior design and dimensions of this lip can vary somewhat as long as the interior of the lip has the required design to catch the bead.
