Lower body discomfort: Saddle issue or just not "broken in"?

[ny biker]

I know people say you should sit on the saddle like you are in a chair and then without rotating your pelvis, hold the handlebars...

I've never heard this. I try to keep my back straight when I ride. It hurts if I don't.

I usually ride with my hands on the hoods, very very rarely in the drops (the crooked parts).