I agree - I think Dell's intentions were good - the 8910 will take a maximum of 4 ea 16GB modules and when shipping a PC with 16GB only - they wanted to save the consumer the usual practice of throwing their old memory (2x8GB) in a box when upgrading. As far as I know, this is the first PC I've owned that doesn't require a pair of modules to function.
My pain was that I bought the option with 24GB from the factory. They use 2x8GB plus 2X4GB to reach 24GB, so no matter what, if I want to upgrade I end up discarding modules. Those of you griping about having just a single 16GB module are actually in good shape, assuming you can find a good match for the existing 16GB module. All of my memory is Hynix, which I think is Hyundai RAM.