To transfer files from a Mac to an iPhone/iPad through a USB cable, use the following method.
First, connect your Mac and iPhone/iPad with the USB cable.
Select the iPhone/iPad when it appears in the Finder sidebar.
Select Files in the button bar.
A list of apps to which files can be transferred will be displayed. Drag a file, multiple files
or folders to the corresponding app.
This is documented in the following article from the macOS User Guide.
Sync files from your Mac to iPhone, iPad, or iPod touch
What surprised me this time was that the progress of the file transfer was displayed!
Until now, when transferring a file, the file transferred was displayed in the application folder upon completion, and the progress during the transfer was not shown.
It was strange that there was no indication of the progress of a file transfer, especially in the case of Apple products such as the iPhone, where icons and animations clearly indicate the current status.
However, the other day, when I was transferring a file, the progress was displayed.
This feature must have been implemented in macOS Venture 13.4 or a little earlier.
It is nice to know what the current situation is.