The way I understand it Kokyu nage are 'breath' throws - or 'flow' throws. It's the types of throws that we do in order to single out the principle of allowing the power of uke to go forward in a simple manner so that you as nage focus onbody movement, breath and not obstructing the momentum of uke rather than on doing a specific lock or throw.
Tenchi nage is sort of a weird in-between technique as I see it. It's based on kokyo to a large extend, but also requires some rather precise hand movements/positions in order to work. I will allow it as a kokyonage at a grading, but there are so many others to choose from..
Hope it helps
Also.. google is your friend: