I’ve been using slow cookers for ages. Decades. I have put a great deal of effort into getting the temperature in them up to boiling point, so the contents were simmering nicely. Because I thought I needed to.
More recently though, I have been cooking things sous vide, where the meat (or whatever else it might be) is held at the temperature for “doneness” for a couple of hours or so, and then flash fried on the outside.
Today, I am slow cooking beef brisket. I browned the outside of the joint in a frying pan before putting it in the slow cooker, as you do. While I was waiting for the liquid to boil, I realised that I do not have to! It only needs to get to the “done” temperature… As long as the other ingredients are cooked (and after nine hours I think they will be) all will be well.
I expect that if I tell people this, they will shake their heads, and say “Surely everyone knows that?” I looked for introductory slow cooking articles online, to see if I could confirm this insight, only to find an article that insisted the slow cooker should get to 150°C for brisket. It must have been written by a machine, using source text about cooking in a smoker, I assume.
