This documentation covers the configuration settings for the Sign In page. It explains how to adjust the settings based on whether the login form uses email addresse or username as description text for the Email inputbox or username.
The setting is by default set as enabled, to disable this setting follow the below steps:
Go to profile configuration file
Enable or Disable the setting:
Locate UserManagementSettings > UserNameAsEmailAddress and set it to false
If the setting UserNameAsEmailAddress is not in the file UserManagementSettings then add it as below:
<UserManagementSettings>
<UserNameEditable>true</UserNameEditable>
<NameEditable>true</NameEditable>
<UserNameAsEmailAddress>false</UserNameAsEmailAddress>
</UserManagementSettings>
...