Forgive me, but as it’s a regional app, it’s rather niche and as such I’d say unlikely to be included in the WiiM app, but who knows? OK, you might argue the BBC is regional but it’s there (albeit a weak integration) but I’d argue it has a wider reach
Also, as I’ve said before, I think it’s unreasonable to expect the WiiM home app to be the all-singing, all-dancing universal app for all services, even for the ones it currently supports for a variety of reasons. One of those reasons is that the native service apps, take Amazon Music or Qobuz for example, usually are more feature rich than the interface they supply to third party app developers like Wiim - if indeed they do have such an interface for third parties to use. You more or less confirm that by saying the Radioapp is better than TuneIn.
I’d also say WiiM devices support Bluetooth, AirPlay and Chromecast precisely for that reason - to accommodate apps that don’t have a third party interface or which are unlikely to see an implementation in the WiiM Home app.
Personally, I’ve tended not to use the WiiM home app for anything other than configuration and tend to use the more feature rich streaming services own apps.
I’d also say that using Alexa to directly deliver to the WiiM device the stations the app supports isn’t a bad compromise
Cheers