Hmmm, alright maybe not terrific examples of etiquette because you're right, both of those are in the FOM.

How about nodding to other pilots in the terminal and introducing yourself at the gate, both etiquette that other pilots expect but aren't written in the FOM. Better?

Point being, there are things other pilots expect of us that aren't in the book. Are you required to do those things? No. But like it or not other pilots may judge you for it. Whether you care about their judgment is your choice.