the sum of the initial ratings: usually, but not always 3

In general, starting ratings choices add to 3. But of the playbooks in the rules, Snoop, and Exile, the Mundane is the only one for whom all of the sets of ratings add to 3. There are a few 4's (all of the Exile's are 4), and a bunch of 2's.

Is all this deliberate?

Yes.

When I give someone a second +2, that gets counted as 3 points.

Plus, some of the hunters have implicit moves giving them more (or less).