iTexthub application is designed on a distributed pattern. Multiple components are hosted as an individual service for better scalability. For example, CDN is hosted as a stand-alone app so that both User and Admin panel share it. API is also hosted as a standalone application.
In view of the above if you are installing SSL, it should be a wildcard. And every new wildcard SSL configuration is to be populated in all the applications, due to which WILDCARD SSL certificates are required.