The third act of a massive blockbuster like Avengers: Endgame can be a constantly changing and fluid construction, as well.
Yes, co-directors Joe and Anthony Russo might know well in advance that they want to create a scene where Spider-Man rides through the air thanks to Mjolnir, but the choreography of the sequence could go through multiple iterations before it’s finalized.
This also explains why Giant Man can be seen fighting in the background of the Attack on Avengers Campus scene, even though it had been established that Ant-Man (Paul Rudd) and The Wasp (Evangeline Lillie) were in Scott’s van, trying to fix the Quantum portal.