How to only show a child age appropriate games?

Did you not test what I said or did it have no effect?

Thank you for contacting us! I'm Anderson, an Independent Consultant and a Microsoft user like you.

Good Morning

For access you must change the way to enter the xbox, from all accounts, the child enter with the control and adult change to enter only with the password. see how here:

https://support.xbox.com/en-us/help/account-pro...

see how to also manage the child account privacy settings:

https://support.xbox.com/en-us/help/family-onli...

I believe that only logging into the child's account should only show the games allowed for them to play.

I think the closest you get is managing the games by your child's age.

Here is a guide for it:

You can set your child’s age, which Xbox One uses to control the child’s access to specifically rated games, movies, TV shows, and music. By default, if the child is under 8 years of age, Access to content is set to “Off.”

To change the default setting for your child:

1.Scroll left from Home to open the guide.

2.Select Settings.

3.Select All Settings.

4.Under Account, select Family.

5.Select the child account you want to update.

6.Select Access to content.

7.The content limits are unrestricted for all users over the age of 8. You can select preset age-appropriate limits by choosing your child’s age from the list. We’ll show you what the presets are for that age. You're not restricted by date of birth—you decide
which maturity level is appropriate.

What is the appropriate age where it is not longer "Child?"

You can only disable the controls by logging into the parental account and changing the family or settings for the child account from that account unless you reach the appropriate age to become an adult account.