Copyright law is a fascinating topic. I considered (note the past tense) myself well versed on it, but this issue has brought up parts I was not aware of. Before retirement, I was a professional engineer. I reviewed and signed off on code copyright filings and software patents. I'm also a multiply published photographer, who has had to deal with infringement of my works, and non-exclusive usage rights issues.
I wasn't aware that recipes were not copyrightable. But I should have expected it. Formulas and processes are patented, not copyrighted. And a recipe is simply a formula and process for making something edible instead of steel, a battery or more timely, a vaccine. Unfortunately, while copyright (in the US at least), is automatic from the moment something exists in fixed form (printed, emailed, recorded, etc.), and relatively inexpensive to register, patents require extensive, expensive legal work. That's fine if you are patenting a way to make a great battery which will make millions or billions. But you can't very well aplly for 100 patents, 1 for each recipe in your cookbook! The filing fees alone, without the preceding legal work, would kill you.
So I am left with a little confusion. I remember an article from years ago about one brother suing another for infringement, when they had both used family recipes to create restaurants, and one had copyrighted the recipes. I think I remember the judgement being that the sued brother must change the recipe by 10%.