With those two as the examples, I'd definitely agree with that. I'd regard both as frontend frameworks and I've never heard Next described as a SSG, though, but Gatsby seems to be used as such by fans of reckless overengineering (because I definitely need GraphQL for my blog).

Eleventy would be quite a bit closer to Hugo/Zola, but even then you'd have to use npm/npx to install and run it.