In 11.1 can't make iTunes purchase if restrictions used to lock account settings

For years I've had a child's iPhone configured with a restriction so they couldn't change account settings. Purchases require me to enter my iTunes password.

With 11.1 (maybe 11.0) this stopped working. Now account settings can't be locked; if they are locked clicking on the submit button for a purchase does nothing. If they are unlocked the purchase proceeds.

It's a bug.

#bug #ios11