I think that's a fair point, but there's inevitably a ton of randomness in how large groups react, and also inevitably differences in how people see individual cases. So that probably would be true no matter what.
It's mostly a moot point, though, because for most users there's bound to be at least one story that is (a) clearly on-topic and (b) clearly not apolitical.
Except i don't think it is a moot point, because my thesis is that the HN community perceives certain things as "political" and other things as "not political" and that it creates a bias. Obviously individual users are going to have different opinions in some cases; HN isn't a hive-mind. But that doesn't mean one can't predict trends in what's going to be flagged as "politics" and what isn't, regardless of the actual political content.
It's mostly a moot point, though, because for most users there's bound to be at least one story that is (a) clearly on-topic and (b) clearly not apolitical.