The low number of reallocated sectors suggests that the NAND deserves much of the credit. Like all semiconductors, flash memory chips produced by the same process—and even cut from the same wafer—can have slightly different characteristics. Just like some CPUs are particularly comfortable at higher clock speeds and voltages, some NAND is especially resistant to write-induced wear.
The second HyperX got lucky, in other words.
So it's definitely possible that the 840 Pro has reliability problems even though one of them won this test.
Even if you don't know that, basic stats should tell you that testing a single unit from each manufacturer is going to be meaningless at best, misleading at worst.
Is less expensive than testing a dozen drives of each model, and better than testing no drives at all. It's not meaningless at all; it just has to be read with the right caveats.