I'd like to think that most people that disable "Search as you type" wouldn't expect this to occur and would find it to be undesirable behavior.
In my case, sometimes I will type something into Everything and see an autocomplete come up and show me that it's something I've searched for in the past. Often this reminds me that I found or didn't find what I was looking for (most commonly with
content:I only recently noticed that this still saves what I had partially typed in into my history. I think, when "Search as you type" is disabled, it should only ever save it into the search history when the search is actually activated, but I could certainly live with an advanced setting that does this instead.