I think that chart has mashed the current generation with the next one. Those X Elite and Plus models are the current ones. I do believe that the next generation of Qualcomm chips will be big.Little, but while the current ones had an 8+4 config, they were all the same core.Here is an image that seems to suggest three versions of the SoC
It looks from the chart as though Qualcomm may be going big.little in some of the second gen. The linked site is difficult to read, as the text is mostly Hangul.