This is disputed. There is scientific literature that shows that additional study helps. See here, someone has researched the effect of additional study on SRS.
First: what is this thread about? Well, something I’ve seen regularly posted in the WK forums is that doing any reviews outside of the scheduled ones will actively harm your learning, which sounded strange to me. I spent much of today delving into research of the field, and the post below is my findings. There will be a tl;dr at the end of the post.
Let me give a disclaimer. I don’t do research in this area, nor do I know anyone that does. This is primarily just what I got from reading two meta…