Transfering files from an iphone is a nightmare, I used to transfer files using rsync in some app that worked as a linux container, but I first had to transfer the files to the app's storage.
In iOS, apps can only acces a directory specific to them that no other app can read, there are no shared directories that all apps can acces or a way to make symlinks or something would help (at least i'm not aware of them). So I have to move my files from wherever i need them to use them (like a video player app whose directory is not visible to the file sharing app) to the directory of the app I use to share files, and viceversa when I share files from a computer to the phone.
In android, I can give apps permission to read and write files on the general storage.
I'm talking about files in general, I never tried to share voice notes specifically.
If you only want to transfer files to the PC and not to the phone, I think the files app supports FTP. If you can access your voice notes from the files app, this is probably the best solution. File transfers lver USB on iphoes are extremely slow anyway.