Looks like the guide is using it to install the Hugo binary and Git. So if you already have git and a Go dev env, you shouldn't need to do that.
...they refer you to the GH's releases page, where you can find binaries ready to use (I don't use Mac, but I see 64 bit and ARM64).
You don't need a Go dev env to use Hugo. I use it in Linux and I don't have a Go compiler installed.
Basically it uses the Go dependency manager to help you assemble your website. Here's my documentation on Hugo modules for my work-in-progress Hugo theme: https://git.sr.ht/~skyfaller/maxethics-hugo#hugo-modules