"When you backup and restore a QB Desktop company file, you are able to select the file path as to where to save that file.  I am presuming that the related peripheral files that you mentioned (extension types - .tlg, .adr, .nd, .dns, etc.) are saved in that same location as the company file."

You can Look at your own computer system. You will see subfolders and files, and the "company filename" from the Windows file is part of the Naming of the associated utility files and subfolders. When you Restore a Backup, you will also see a folder that is created for "Restored_XXXcompanyNameHere_Files" and in this subfolder you Also see a file named "HowToRestoreExternalFiles.txt" that basically is a ReadMe file.

"So why would OneDrive be any different than saving that file to any other file path location?"

You are relying on Synchronization, which is not the same as "database pointer" tracking.

"In other words, why couldn't a user still use the QB Desktop file that was saved to the OneDrive location (just like any other file path location)?"

Well, one of the biggest issues is the .nd and .dsn = Data Source Name and Network Data tracking, which keep track of "who" is in the file, by computer. That is why Multi-user = concurrent use, is managed by the Database manager hosting app installed on a computer.

It's not Just Like Word and Excel. It is required to be Managed, as I explained, because it is a relational database.

"Forgive me if I am missing something technical, but I very much appreciate any further response you can offer on this topic."

It is Very technical. I copied this text and kept it for reference, from another forum topic, for why you cannot use a NAS (network atteched storage device, or Sharing an external drive in the office):

"We have to be very precise with our terminology. There is a difference in the implications of iSCSI vs just mapping a drive. It's not enough to say Quickbooks supports or doesn't support NAS devices. It doesn’t support Unmanaged devices. People who don't understand the implications can get themselves in trouble, corrupting their company files.

This also is why Static Storage such as DropBox and One Drive cannot be used.

There is a big difference between a standard NAS and Enterprise Storage.  Quickbooks needs to run on a Windows host that has "exclusive block-level" access to the storage.  There is a big difference between a device that supports Fibre-Channel and iSCSI, vs one that supports SMB, CIFS, or NFS.  

Unfortunately many "wonder machines" depend on the user to know the implications and drawbacks of the different devices.    It's one thing to have a file server to share movies and general documents.  It's quite another to host a database.  Quickbooks is a database.  Or, more specifically it is an application built over a Sybase database.    SQL-Server and Oracle have the same issues running on an external device."

"As you noted, we are otherwise considering a solution like QBox for sharing the company file with clients, but are wondering if that is even necessary for my business partner and I to share the file within the same office from separate PC's.  Thank you again!"

I am glad to offer QBox, but that would be used for sharing Not from the same office. We though you needed access from two computers Not Located near each other. It is a Coud location.

In the Same Office and wanting to share a data file = Multi-user.

Both computers install the QB program = you pay for two licenses or "seats." One computer is Hosting = installs the Database Manager hosting service, an app that runs at startup, and you don't need QB open on that File Hosting computer. Both computers Wired via an ethernet network, even if peer-to-peer through a router. You set up usernames in each file. Your Windows user needs to be Local Admin on the hosting computer, even if working from the "other" computer.