JujuLautre
Deity
Interesting. I think its broken then, cause while I had traded fro Philosophy, I could offer it to Portugal many turns later. I think I actually received Philosophy from a GP.
When no tech brokering is on, AIs are reluctant to trade for techs they are finishing, because it means that they would not be able to trade them. So it could be that the AI was on its way to philosophy.
This feature is here to prevent the exploit "when you are at one turn from completion of your tech, I give it to you so that you will not be able to trade it"
I believe that if you hover the tech in the diplo screen, the message will be different (like "we would not gain anything...", I don't remember, did not play with no tech brokering in ages)