So if I understand correctly, a good strategy to avoid WFYABTA is to trade extensively with the first civ you meet on a new continent (although a good diplomatic strategy is to meet everyone first before deciding with whom to trade).
You are saying that if if I know A, but not B, and A and B know each other, B doesn't give me WFYABTA for trading with A. I thought (don't know for sure) that B will give me "you have traded with my worst enemy" diplo hits in this situation. Is that correct? I think I remember having negative diplo with a civ I just met because of this.
Moreover, you are saying that the landlocked civs on my old contintent will give me WFYABTA for tech-whoring on the new continent. So I'd better get what I can from them first if I'm close to WFYABTA (although I'm not going to hold off on meeting the new continent).
Also, strategy-wise, this means you want to trade with the tightwads like HC before you trade with Mansa.