I'll post a paraphrase of what
@Anders_ASUS said about this the last time it was brought up. The situation hasn't changed since then.
We don't have enough software resources to support a completely separate team that works just on Indian FW updates. Since India is the only region with this technology at the moment and we can't support it properly, we have chosen not to. If it becomes a more widely available technology or we have the resources to properly support it in the future, this position may change. We understand that the feature is a popular request and are always listening to your feedback.
The complete thread is here.
https://zentalk.asus.com/en/discussion/7926/vilte-or-native-video-calling/p1