QB uses a Relational Database for the data file, and it is not Stand-alone; you overlooked that there are associated Utility files that get Live Updated while you work. That is why Multi-User (concurrent) has to be Managed = Database Manager Hosting app. Even if you are scrupulous about having only one computer at a time using that file stored in a Static (fixed) storage location, you still see those Utility files being updated, to keep track. That includes .tlg, .adr, .nd, .dsn, etc.

Unlike Word and Excel, nothing about the datafile is loaded into Local Memory and then put away when you are done. You know this, because in Word and Excel, you need to have Saved, or Saved at the end, before the file is Closed. But, as you work in QB, every single transaction and entry requires you to Save and Close or Save and New.

You cannot use DropBox, One drive, Google Drive, etc.

You can research QBox; this seems to be the only Managed Shared Storage for using QB data, as a managed relational database, that avoids creating conflicting data files.