My experience in having trained in aikido for many years, and with dozens of different teachers, is that the claim that the strongest technique in aikido is how to become friends with one's attacker is not supported by the training I have encountered in the large US aikido organizations, nor is the ability to perform this 'technique' manifest amongst either the leaders or membership of these organization. Many of them cannot even get along on a friendly basis with people are who not attacking them.
I guess I understand, what you are saying.
The short answer is, if you haven't recognised it, you might not be ready for it.
The difficult part is to explain it in a way that you might get an idea of what I mean, if I say it.
First of all there is no specific technique to befriend someone. It is embedded in every technique. A hybrid form of this effect might be kokyunage. There are some techniques, which are taught as kokyunage, but at the same time, kokyunage is embedded in every single technique, if it grows to perfection and training any technique improves you kokyu power and thus teaches you kokyunage.
Befriend someone is not taught explicitely, but in every technique you should learn that the first goal is not winning, but safety - your safety and your partners safety. Sometimes you might learn some variations to overcome even an unompliant aggressor, but that could be some necessary intemediate step (some might disagree with this part) but it is never the final goal. The final goal is always to find a way to protect your health as well as the health of your foes. And that is not even the techniqque to make friends, it is just the first step. But steady training and hopefully a series of 'small enlightments' will lead you to that goal.
Tha last sentence is probably the part hardest to explain, becaus it realy shows, that many of us have not gone very far on this path - including me, but I am still starting. I cannot argue on this one. Probably it is as difficult to explain as why there is all that pain in the world.
Another thing to think about. BJJ is the standard fighting training in the US forces. but only very few American soldiers ever need to submit an unarmed person in a grappling situation. So either there are only fools in the Pentagon (please do not start the discussion in this point) or they expect something else a soldier can learn from BJJ. I guess Kevin Lewitt told us already something about this. If I recall right it should have to do with keeping a clear mind in difficult and stressy situations. But whatever it is - you won't find any technique in BJJ that obviously teaches exactly this.