Of course it's not sufficient. I don't even think it's necessary. But, generally speaking and in my experience, formal algorithms knowledge is incredibly useful, and you are at a significant disadvantage if you do not have it in your toolbox.
Of course knowledge of algorithms is useful.
I was pointing out that a specific correlation you mentioned wasn't particularly robust, and certainly didn't amount to the causation you were implying.
Perhaps I should have made my point more explicit by noting the existence of counterexamples - engineers that design and implement good APIs without any particular knowledge of CS or the implementation of sorting algorithms.
You actually are conceding my point when you admit that knowledge of algorithms isn't even necessary.
I've come cross more than a few "can write a sorting algorithm" engineers that nevertheless design APIs requiring server-side session state, or that have gone ahead and implemented a sorting algorithm embedded in the server-side HTML template.
Knowledge of algorithms is not a panacea.