Onedrive App Security Issue on Apple Devices

I have the Onedrive app on my iPhone and iPad devices and have enabled passcode on Onedrive (as well as the iPad security) for further security measures (in case someone steals or breaks into my apple devices). The major security issue comes when I also install Microsoft Word or Excel on my iPhone/iPad devices; MS Word can search and open Onedrive files/folders without the passcode. This is an easy backdoor and makes the Onedrive passcode security feature useless. I could use the Vault option but if I do need to use a file in Word (or any other MS product) I am unable to see the Vault directory within the MS Word app. Plus if you access the Vault through the Onedrive app, you cannot edit any file. I could also remove Onedrive from the Word app, but then again it makes the Onedrive access useless.