app store still requires a password when require password free downloads is off?

Hi

My daughter has a 5C running iOS 8.3. I have set up restrictions so the Password Settings option is listed under Restrictions rather than iTunes & App Store.

The problem we have is that even though Require Password for free downloads is off, we are still asked for a password for the Apple ID registered against her App Store when she downloads a free app from the store?

Are there parameters that define 'free' download (e.g. totally free - with no in app purchases)? This doesn't seem to happen all of the time - and I notice that apps which have in app purchases seem to require the password - even if they are free to download.

cheers for any help.