Expert Level 1
When asked about when mobile will have HD streaming, this the answer from Amazon:

I get your concern regarding the HD content on Prime Video. The streaming video quality for android devices is up to Ultra HD. For more information, kindly refer to this link:

Mobile Devices with the Prime Video App

The Prime Video app is available for devices running Android and iOS.

Note: Supported features differ based on the specific model and configuration of the mobile device being used. Not all Prime Video titles support all features.

Android devices

Streaming Video Quality - up to Ultra HD

Sound quality - up to 5.1 surround sound, Dolby Atmos

Closed Captions (Subtitles) - Yes

Live Streaming - Yes (on the latest Prime Video app)

Audio Description - Yes

Live ad support - Yes (on the latest Prime Video app)

Ad supported channels - Yes (on the latest Prime Video app)

Support Website 


...... So doubts are clarified. 
1 Comment
Expert Level 4
What? I didn't understand...
I too had a chat and email with amazon they said that restriction has been lifted and we can watch HD content on both mobile data and WiFi. The thing they said to me is there is no issue with app please contact Samsung and gave me Samsung cc number🙄🙄