I noticed it as almost insignificant as well. I imagine though that it has more too do with the increments being insignificantly small versus it not having any effect. The CPU frequently trades 20 tech when I am generating 30-50 per turn. I generally reserve trading tech directly as a diplomatic tool now.
It may be a bug though. I would recommend doing a test and saving the before and after (trade) with the "print screen" button.