Lip / Mouth Movements Too Exaggerated

I am noticing many of the mouth / lip motions are too exaggerated - body expressions also lacking emphasis, often breaking geometric alignment.

[Referring to one I tried in my own voice, with a photo of myself - my accent being UK British]

But in effective speaking vowels would be created internally, with the jaw simply springing open for these - while any mouth or lip movements reserved for consonants only.

A helpful resource in all aspects of vocalization: manual accompanying the Jeannie Deva Contemporary Vocalist Course (the word 'contemporary' here meaning "since the modern era discoveries in human anatomy")