Cooking moderators are diligent about managing scope / valid questions. I am not questioning current scope.
May I ask if that was the scope going into beta or during beta did you find the need to limit scope (e.g. recipe)?
One small correction: this isn't a moderator thing. We have plenty of users with enough reputation to help close questions, and the site scope was decided by users, not just moderators. We moderators also contribute in this regard, but we're not in charge of site scope.
Generally, the details have been refined over the years, but we haven't added a lot of big categories. Recipe requests, career/business advice, winemaking/homebrewing, and health/nutrition have all been off-topic from the original FAQ. We also decided about "what can I make with X?" (aka culinary uses) very early on. Initially we were a little lax about including "what goes with X?" under that banner, and had some things slip through, but eventually we ironed that out.
That said, while we knew all this in theory from the beginning, a lot of things slipped through in the first year or two, especially things that were less obvious about falling into one of these categories. You may still be able to find open questions on some of these topics if you go digging. However, the things that did slip through often didn't do very well: questions with a bit of "what to do with X" would frequently end up with a large number of answers that voting struggled to rank well, questions with a bit of health/nutrition involved would attract dubious unsupported claims, and so on. Over time, we got better at consistently enforcing our rules, and perhaps slightly extended our notion of what falls under each. Notably we've gotten stricter about pairing questions ("what goes with X") which in hindsight aren't really much different from "what to do with X".
Note that there weren't originally custom close reasons for any of this; that feature was added later, at which point we selected a few things that we were already closing routinely and added custom reasons for them.