Interesting. According to the spec sheets for those DIMMs (here
), the "non-H" version differs from the "H" one in only two ways: 1) it uses 0.6W less power; and 2) the "tRFCmin" timing parameter is 50ns less. I can't imagine the power consumption being the issue, so if you really had the two different variants, I guess your motherboard just doesn't like the higher tRFCmin on the stick you returned.
(Side note: The higher power consumption may also explain the larger PCB. They may be relying on the larger PCB surface area to act as a heatsink, to get rid of the extra heat.)