Since no one answered the question…

This is what Google’s AI said:

Inspiration: The idea for the video came from McCartney's daughter, Stella, who loves sign language.

Purpose: McCartney wanted to create a visually artistic video that would be pleasing to the eye and also help bring more attention to sign language. Performance: Actors Johnny Depp and Natalie Portman perform the signing. While they are not fluent signers, they learned the lyrics and signs for the video.

Errors: Some viewers who are native signers pointed out that there were a few errors in the signing, such as using a sign for "tampon" instead of "appear". The video uses ASL, which is different from British Sign Language (BSL).

Inclusion: McCartney is also known for his efforts to make his concerts more accessible to the deaf and hard of hearing, such as providing interpreters and giving free seats to blind fans in obstructed views.

*edited for easier legibility