Instead of raring your own files, you can set up unity builder to create and upload for you to itch, and users get auto updates and no extract needed. I am also a unity dev and can show you how if you like, but it is so much easier than manually putting up builds.
Consider using unity super builder with butler for itch.
Just to clarify, you're telling me that there is a way I can update the executable files that users downloaded previously?
You can set it so that users that are using itch app to properly auto update when you release a patch using unity super build and butler. It does proper versioning and creates kb sized patch files for games that adjusts the contents. And you don't have to manually put the files up on itch.