Norton Identity Safe: iphone mobile - security issue?

Hi, I tried many app for password storage and Norton has many chance to become one of the best.

But:

iphone app:

1) I open my vult with a pin

2) search for a password

3) put app in background using home button (i forget to close the vault)

4) anyone can restore app from background and read my codes

 

All  other apps (password manager, mobile banking and so on..) ask for the pin both in opening app and in restoring from background.

 

Why is NIS not adopting this secuirity feature ?

 

thanks