There is an issue with tech trading where civilizations can trade tech when they don’t have the prerequisite for it. For example, giving/receiving "medium hulls" when they/you haven't discovered "small hulls". Its like teaching someone how to run before they can walk, or teaching a primitive civilization how to build aircraft before they have discovered the wheel. It also makes tech trading unnecessarily confusing due to the sheer number of techs that show up to trade. You shouldn't be able to give/receive a civilization a tech unless they/you have the prerequisite first.