Cannot filter on Demographic Locale in Amazon Pinpoint

I am trying to filter on an endpoint's Demographic.Locale attribute based on the description here. I am passing them in IETF BCP 47 format (ex. en, ar, id).

If I call the get_user_endpoints API using boto3, I can see the correct Demographic.Locale field in the response. But I cannot see a "Locale" filter in Amazon Pinpoint when trying to create a segment, I can only see:

• Platform
• App Version
• Make
• Model
• Country

Is there a reason Locale is not exposed in the Amazon Pinpoint segment filtering?