The thing is that "how many people are incarcerated" is basically just a random trivia question, whereas the "Minister X is proposing policy Y [..] what is the incarceration rate?" is a specific political questions.
Some examples of questions that could have a "political hook":
- How much coca-cola do people drink? Banning soda drinks is a political topic
- How often do women use sex toys? Sexual morality has been brought up by numerous politicians
- What's Donald Trump's favourite Beyoncé song? important question, apparently
- ...many more...
There are many "trivia" questions you can think of that don't really relate to politics directly, but do have a "political hook" if you look hard enough. Obviously we need to draw a line somewhere.
Another problem with these sort of "just the facts ma'am"-questions have is that "X number of people are in county jails" could probably be used to prove any number of points, but that won't really explain anything as the entire matter is much more complex than that just that number.
Depending on what exactly you're asking more context on can – and should – be added to the answer(s).
To be clear, I'm hardly in favour of naked rants thinly disguised as a question, but on the other hand some context and explanation is useful because it:
- helps set context on how to interpret this number, so that an actual political answer can be given ("conservatives typically interpret this as meaning such and such, while democrats typically think it means such and such");
- explains the author's thinking and can be very useful to help understand the specific confusions or misunderstandings that the question's author may have.
Without this sort of context, questions can quickly become trivia or semi-nonsensical.
In this meta question the accepted answer says that this is off-topic
Well, that question is hardly "accepted". It has four upvotes and two downvotes which is hardly a "community consensus" on the matter. Personally, I wouldn't downvote or closevote this particular question, but it's not exactly a great question either.
It also seems like the sort of question that can be answered with a quick internet search, and doesn't really require any "expertise" beyond basic internet skills (I'd sooner close-vote it based on that).