No, that happens in unmodded games just as well.
Population in F8 is population points, say 12 in a fully developed city. Population in F11 is population as adding the population of all cities together. The population of a city does not scale linear with its population points, it scales much stronger. So a size 20 metro is worth much more than 2 size 10 cities.
Area in F11 does include sea, area in F8 does not.
Although the Demographics screen isn't really useful, many people are curious as to what those numbers really mean. Many people had theories and could figure out by themselves how some of them were figured. Here is my analysis after extensive testing in the debug mode for PTW: Approval...
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