I believe the reason for that issue is that the Hisense app is a pretty dead platform.
This app hasn’t been updated in quite some time (hence the differences in how things are structured there). From what I understood, the app basically connects to a single server and shows the libraries of that server.
The app itself appears to be no longer maintained (no more updates, fixes).
So if you want to have the same Plex experience as on your other devices, you might want to look into upgrading your TV with a modern streaming device – e.g. an Nvidia SHIELD, Apple TV 4K, Roku, some solid Android TV box… (maybe not necessarily a FireTV).
