You'll need to downloadVGMToolbox r1045FSB5 Splitvgmstream
Extract VGMToolbox and then run it.
Go to VGMToolbox > Misc. Tools > Extraction Tools > Generic > Advanced Cutter/Offset Finder and use the following settings as shown.
This will allow you to batch process multiple files to remove the data before the FSB header instead of doing it manually one by one using a hex editor.
Note: You will need to drag and drop the files onto the "Files to Search" white box found in the middle top left in order for it to work.
Extract FSB5 Split.zip to a new folder and copy all of the new .FSB files VGMToolbox made for you into the FSB5 Split folder and run the 'Batch.bat' file.
This splits the single FSB5 archive files into individual FSB tracks from that archive.
Extract vgmstream-r1050-1393-gbf8534a-test-u.zip to a new folder
Copy all of the individual track FSBs from the FSB5 Split folder into the vgmstream folder then run test.bat and it will convert all of the FSB files into WAV for you.