It's better to make sure the pycache folder is empty, to avoid the risk of cache state being shared between multiple users

Could you tell me more details? I cannot imagine any difference before and after about current setting can make shared cache. I know / prefix notate the strict directory, but no idea how it goes further like that.

If the pycache folder is unintentionally shared on Git, it can be downloaded by multiple users who might read someone else's cache or mistakenly consider it their own.

Yes, I got that point. That's why __pycache__ was in .gitignore. I wonder what is the additional "better usability" by this change.

To exclude a folder (anywhere in the project), use: folder/ (for Linux, Windows and macOS , Git is platform-independent in this context)

...if this is the right answer for the question

That's not the answer for the question. __pycache__ is already in the .gitignore file. Directory notation narrow the filter down only to directory, to allow __pycache__ file to be added to git.
I doubt this change give any kind of "better usability" as described in the PR body in practical scenario. Please leave a comment if you can make one.

I merge this not for better usability but to describe the gitignore intention better they were expected to be directory.