Implemented somewhat yeah, but I think it's sensible and more discoverable having one here as you say. :)

On 14 September 2023 07:51:02 BST, Juri Linkov <juri@linkov.net> wrote:
>> A small patch to introduce a function from projectile that I feel is
>> missing, please feel free to yell at me if this has already been rejected
>> :)
>
>Thanks for the patch.  However, this is already implemented in
>'save-some-buffers-root'.  OTOH, having a separate command
>maybe be not so bad.  It could be bound to 'C-x p C-x s'.