As of the R3 2019 Release of Telerik UI for Xamarin, Day View and Multi-Day View are the only two views where Appointments can have custom data templates.
This is done via setting Appointment Content Template to a template selector in the Day view or Multi-Day view settings object.
It would be useful to add Appointment Content Templates to the Agenda View, allowing for finer customization of the appointment. 
Similar to Day View and Multi-Day View, it could be set via AgendaViewSettings.
Agenda view has differing functionality from Day and MultiDay view which makes it better suited to certain user experiences, however it is currently limited and missing the same appointment customization options that the day and multi-day views allow.