On the Print... dialog, "Print to file" is one of the items in the list of Printers. It should be an option separate from the choice of Printer. Open Notepad. Select File -> Print... There is a checkbox for "Print to file", separate from the listbox showing the available print queues. I can choose a printer, and capture a print-file formatted for that printer. In LibreOffice, "Print to file" is shown as if it were itself a Printer. I can only capture a print-file formatted for the current default printer.
Virtual printers are common, so I don't really understand this request. Let's ping design team for democracy's sake.
Current work flow is acceptable and consistent cross platform. Set an OS driven default printer, then select the Print to File action from the LO Print dialog. No compelling reason to implement the "Print to File" printer selection within the print dialog.