I have used the chrome profiler to identify the Layout shifts on our website and discovered that the Google One Tap banner is causing a significant layout shift (> 0.1) on mobile (Image of profiler showing layout shift). I have also added a Performance Observer using layout-instability API to identify the component causing the CLS, and it also indicated the same.
I have tried changing the position of the one-tap using data-prompt_parent_id, but this is ignored on mobile web browsers as mentioned in the developers guide.
You might try to re-test, recent improvements have been made to reduce or eliminate layout shift and improve the CLS score for Core Web Vitals.