AMP obscuring the URL is a side effect of the current technical implementation, not a goal – and they are working to fix it: https://searchengineland.com/google-announces-signed-exchang...
Then Google relented and provided a non-solution in the form of an obscure bar on top of AMP pages (in which the link to the original page is deliberately designed to not look like a link).
The signed exchanges is a bone thrown towards standards committees after all the damage has already been done.
And the "solution" has been directly called by Mozilla harmful, they are not going to implement it. Safari shares Mozilla's concern.