FlexOrgs are part of the default settings for new tenants and as such new tenants that are created will use Usergroups, Role Documents and FlexOrgs rather than the classic Roles and Organizations.
When a new Flex user is created, it defaults to the standard role under the classic Roles and Organizations.
To double check the users Usergroup membership:
Navigate to "Setup -> Admin -> Usergroups -> Users" which will display the Usergroup the user belongs to. See below:
Note: The area highlighted in green above will contain users if any are listed. This example has no users present.
The Usergroups each user belongs to will be displayed under the "User Groups" column. To determine the Role Document they belong to, select the Usergroup and then navigate to the Assignment tab as per the below: