In the movie Arrival, why did China's general have to share his phone number and repeat what Louise told him because he knows she knew them anyways!
OK… this is tough to explain… bear with me.
At the time he gave her the number and phrase, she didn't already know them.
As soon as he told her… she had always known them.
He had to tell her 'now' in order for her to have known it back 'then'.
No matter what time she acquired the info, at some point in her life/time-line someone had to tell her. Because of the non-linearity of time for her after her interaction with the heptapods, she would then have always known/will know it.
Make sense now? or then?