If the web host has several sites for hugo, then: 1. One hugo works for all sites, 2. Each site needs a separate hugo.
Thank you in advance
You need only one hugo executable, and you can generate your sites each from a project folder, which has a separate config file and templates.
What Rick says above, plus: the Hugo executable takes your content files and website theme and builds static HTML files from them.
But Hugo doesn’t serve those static files to website visitors. So the webhost doesn’t use Hugo, and can use Apache, Caddy, Nginx, or any kind of server software to serve Hugo websites to visitors. From the perspective of the webhost it doesn’t matter if you use Hugo.
I wanted to jump in and clarify that, because from your quote it looks like there might be some misunderstanding. Hope this helps.