Hi John,
Thank you for contacting us. Any and all apps that use Touch ID can use Face ID. Please enable Touch ID in mSecure 4 to start using Face ID in mSecure 4. mSecure 5 does have the label set to "Face ID" instead of Touch ID to avoid any confusion here. Either way, both apps can use Face ID. mSecure 5 is also optimized for iPhone X though :-)
John