Did Oppenheimer really told Einstein, chain reaction which results in The End has begun

Did it really happen?
Personally, I love how, in the beginning of the film, we see from Strauss’s perspective that Einstein is standing near a pond & his hat flew off and fell down, which Oppie picked up and handed it to him.

They discussed something that was kept hidden until the very end, where it was revealed, they talked about the chain reaction & how it had begun, but in another context.

Was that real?
Because I got goosebumps.
I love that in almost all Nolan movie, you figure out the motivation or meaning behind all the story in the last scene, where the entire film comes together.

What do you guys think?
What’s your favourite scene from this movie? 🎥