It's difficult to compare FPGA families since the members of the families are available in different sizes and speed grades. It might be that they have compared the fastest/biggest devices in each family though. Still they should tell you exactly which device they have compared. It might be that they have used a different design than the one I've tested. It might be that they have used different optimizations for the different devices. It might also be that they have done a general comparison from other designs and used that to estimate the hashing speed for the various devices. So everybody could be telling you the truth, but all the parameters for the given results have not been given.

Also note that the Stratix V device I used was not the faster nor the biggest available.