[farhanito]

That is correct, or a buggy Dolby Audio licence implementation. Such DD+ Netflix App audio downmixing works fine on FireTV and Apple TV devices.

Yes

Netflix App on approved Netflix media players / TV's = 1080p or 4K all the time.

Kodi Leia Netflix App = 1080p or 4K but only with Netflix Original Content, everything else will be Max. 960x540p 

Huh?
So even on shield, with stuff thats on netflix which arent "originals", you cant watch in 1080p?

i thought on  shield, the kodi netflix addon would do always 1080p or evven 4k for al stuff?

Unless the Shield has got something no other Android - Google Certified, Widevine L1 equipped & HDCP 1.x/2.2 capable device has - well hidden - under the hood.
Then yes - 960x540p is the Max resolution for streaming content that is not- Netflix Originals, when using the Kodi Netflix Addon.

A simple test is "The Meg" movie. This restriction seems to mainly affect movies.

Not exactly. Devices with proper licences like Shield (pre-Pie), Mibox, FTV Stick 4k will stream at max available resolution with hw acceleration. 1080p for non Netflix originals (some are 720p like Jurassic Park III).