Very definitely Bernstein had memorized it all.
I like that lady playing the flute, I think she’s the only one with that instrument in that little ensemble.
I think the video and sound are a little off sync, because I can’t believe Bernstein would be anything other than pinpoint accurate in his beat.
She’s got the Marcel Moyse method going. Flute angled and playing out of the side of her lips. My flute prof played the same way.