Until today nobody knows the actual file format of the files in question. File name suffix means nothing. With LO there is a method to see the filter that was used to open a file successfully. Call menu:File>Save As... and the file type listbox will display the current file format such as "dBase (*.dbf)". Unfortunately, the File>Properties... dialog guesses the file type by its name suffix.
https://bugs.documentfoundation.org/sho ... ?id=145003
When you rename some binary file to odb/odt/ods/odp/whatever, Windows passes the file over to LibreOffice no matter what. LibreOffice has some advanced "file sniffer" which detects that the passed file is not a zip archive (thus no office document) and then tries to detect the true file format by magic cookies or characteristic binary patterns. Unfortunately, LO does not clearly indicate the result of this inspection.