Imagine a compelled to unlock scenario, for example you have a gun to your head, or there is a court order compelling you to unlock the device. It's not plausible that you forgot the password to your main profile, no one is going to believe you can't unlock it.
However, it is plausible that you don't know the password to secondary profiles, I've genuinely forgotten passwords to secondary throwaway profiles many times.
If someone compelled you to give them access to your main profile, can they tell when secondary profiles were last used? Modified? Created? If they can, they can put serious doubt on any claims that you don't remember the password because they can prove the profile was used recently.
Does anyone know if the main profile can access enough info to show secondaries were recently used, or other similar compromising information?
Also, can the main profile tell what apps are installed on the phone and their version number? Even if they are only present on secondary profiles?
The duress password is awesome but could easily get you killed or jailed for violating compelled unlock or evidence tampering laws. So, I was wondering if secondary profiles are a better solution.