You NEVER use the recommended hook size in the pattern. What you need to do is make a gauge swatch to see what YOUR tension is, what kind of fabric YOU get with any hook and yarn.
There is a direct relationship of hook size and yarn size. A large hook means thicker yarn. A smaller hook means finer yarn. You cannot always use any hook with any yarn!!
Now, if you are making something that needs to be an exact size, for example a fairly closely fitting top, or socks, the finished size is crucial. The hook size needs to be exactly right. Other things, like a scarf or a blanket are not that critical if it is a little bigger or smaller than expected. So you need to be the judge. When the pattern suggests a hook size, that is only what the designer found worked for her, but you may not get that same gauge. So you may have to go up or down in hook sizes to get the same gauge, and the same sized article.
I tend to hold my yarn quite firmly, so my stitches are smaller than most other people. I always have to go up about 2 sizes to get the same gauge as they do. It's not wrong, that is just the way I work. So you need to know how you work. Do your swatch first.
If the directions for the throw say that gauge is not critical for this project, it means that whatever YOU like is what matters, since it does not need to fit anything in particular. When you do your swatch, you will also know how wide your throw will be -- you can calculate how many stitches YOU need, and may need to make it with a few more or less stitches to get a size that YOU want. There are no crochet police that will arrest you if you don't follow the pattern exactly! It's YOUR throw, and you are allowed to make it any size YOU want.
You do not need to use that size of hook and you do not need to use that yarn, or even that colour. YOU are allowed to follow the stitches directions, adjusted to suit YOU, and a skilled craftsperson will use whatever tools are needed to get a product that YOU like.