The point is that "mayors of San Fransisco" does not have a single answer, and therefore any answer WikiData provides will be glossing over a mountain of nuance and important distinctions in terminology.
The same is true of a million million different individual and aggregated data points all across WikiData.
In the context of Wikipedia articles about the Western US city commonly called "San Francisco", the concept of "mayor" is sufficiently well defined that there is a single answer to it.
The concerns voiced here sound a little like "What if in a hundred years, GPT-255 has subjugated all of humanity into a hive-mind and the terms 'San Francisco' and 'mayor' are meaningless?"
I was using the singular example from the parent comment. If it would convince you more, I will provide others - though I'm sure you could think of some yourself, if the mood took you.
