Are Amazon "Parental Controls" redundant if I disable "In-App Purchasing"? In the Amazon Appstore settings, there is a preference to enable Parental Controls. When set, this causes all apps (that are installed via amazon appstore) to require the amazon password before being able to make an in-app purchase. You can also specify an optional PIN to use in lieu of the full amazon password. According to the details, this only affects in-app purchases, and it does not hide 'mature' apps or enable any filtering.

Another setting is In-App Purchasing. This preference is active by default, but it can be disabled to completely remove the possibility of in-app purchases.

By default, no password is needed for in-app purchases, and the in-app purchasing ability is active. For both of these permissions, you are required to enter your amazon password to change the permission.

My question is this: If I disable in-app purchasing completely, is there a need to also enable parental controls? 

Since the preference itself cannot be altered without typing in the password, I feel like the Parental Control preference is redundant for my purposes.
In short, you are correct.  Disabling in-app purchasing completely via In App Purchasing option makes password-protecting under the Parental Controls settings redundant.

It's definitely confusing, and could have been better accomplished by having just one setting with 3 options: Disable, Allow, Allow with a Password.  It's possible that these two settings used to work differently on older versions of this app, and developers decided that keeping the settings separate would be less confusing to existing users than combining them.