What tests would you suggest? Here's what I've observed:

Since I've started paying attention, I never or nearly never observed anyone starting a vocal conversation without verbal handshakes, except when coming out of a larger group's conversation. This is true regardless of how well I know them, whether we've agreed in advance to talk, and whether they have something urgent to discuss.

I have slightly better success starting personal conversations and connecting with people relying on hints they offer than by asking whatever questions I want, and when I drop hints they are often noticed and taken up.