@Sato Hi!
Google has strict policies regarding sensitive permissions (SMS included).
In order to handle SMS related functionality, the application needs to be (in general) registered as the default SMS app. Since GUI-O does not need SMS functionality to run, it would be probably quite impossible to convince Google to allow SMS features in GUI-O. You can read more about it here:
https://support.google.com/googleplay/android-developer/answer/10208820?sjid=7843560484419800904-EU
Regards,
kl3m3n