> I can't recommend being intentionally rude...

As I understand, GP is recommending that folks take a risk that their drumming up a conversation might be unwelcome if they are unsure. They're not advocating for folks to harass people who are in no position to chat or who have stated as much.

People can't read minds, so I think we owe grace to the folks around us if they misread a situation and respect your wishes when you let them know that it's you're unwilling or unable to chat at the moment.

While it's great to learn social cues, it's often impossible to know whether someone is in the mood to chat.