Excel can save/open files from the app's file browser, but won't appear in File Explorer

We have a few users who are able to save Excel files to their Documents folder, seen here:
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However, if I try to find, view, or open this same 'AP Aging Report 09-22-23' file from File Explorer, it will not appear at all. I've made sure that 'Show hidden files, folders, and drives' is enabled. The file is only able to be found in the Documents folder from within the Excel app. I've also made sure to check the file's exact folder location within the file browser in Excel, but pasting that folder location in File Explorer yields no results and the file isn't there. The only workaround I have right now is to copy/paste the file from Excel's file browser into my computer's local Desktop folder. This will not be feasible long-term for these users.

I should note that the user does have an active OneDrive account. However, even if I save this file to a OneDrive folder location instead, it is still not visible within the OneDrive file structure or File Explorer - only within Excel. What is going on?

.csv files might act that way.... change from .xlxxxxx to all files in explorer??