@lunk And why couldn't the Manuscripts app do this automatically? It has the information, so it's only a question of moving the left parenthesis a few steps to the right, so it ends up to the left of the year instead of to the left of the first author.
Because there are over 7,000 citation styles to consider. The in-text citation representation of author suppression is not uniform across them and cannot be described with the kind of heuristic you describe above. Given a CSL formatted citation style and the citation formatter component we use, this is the best we can do (which is just the same as other citation formatter tools do to my understanding as well – as noted earlier, please correct if I am wrong).