Look into the numbers in both reports rather than the generalized numbers and letters. Just click on Print Full Report.
The Volvo has substantially lower cockpit intrusion, has less head deflection, etc. etc. etc.
i see what you mean now...however, i don't think it's nearly as big of a deal as you are implying though...for example, the lower intrusion numbers on the Volvo in various points were 2, 2, 2 and 4mm...the Genesis was 7,9,5 and 2mm...while they look like substantial percentage differences, we're talking fractions of an inch here (5, 7, 3 and 2mm difference, with the last favouring the Genesis)...7mm is just over 1/4 inch, so even though numerically the numbers look quite different, in actual real distance of intrusion, the differences are very minimal, which is why both were given the top rating.
for fun, check out the Mazda5 for comparison...35,26,22,21...sounds like a football audible.
http://www.iihs.org/iihs/ratings/vehicle/v/mazda/5-4-door-wagon?print-view