I can't speak for their specific choices, but sometimes games are chosen for the variety of their demands not the specific demand of a title itself, or its ubiquity in previous comparisons as a point of reference. Also, some games tax the shaders more and some games tax the memory more, and some games are poorly optimized resulting in untrustworthy results. They build a "benchmark suite" based on these factors and use it for a good half year or a year. Bioshock Infinite is a demanding and beautiful game at high settings, and was used as a performance target when it was released, so you can compare it to older cards previously benchmarked as a point of reference.
Also, for the high end cards, most of the benchmarks for these are being done at QHD/4K. Because of these newer resolutions, there's a big demand for powerful cards that can run at those resolutions all the way up to 120FPS. Graphics cards makers have a lot of headroom to work with, 50% performance increases would be well received right now and not be considered excessive.