As you pointed out, a JAMstack setup is
- decoupled frontend + backend
- pre-rendered static assets served from a CDN.
A Vue application can be considered JAMstack on the condition that templates are not being rendered on the backend. If your Vue application uses server side JS to load content, then that isn’t JAMstack. However, if your Vue application uses client side JavaScript to load content, that can be considered JAMstack. It’s understandably a little confusing since the definition of what is and isn’t JAMstack isn’t binary. Here’s an article for some extra context on whether a SPA is JAMstack: Can a SPA be JAMstack? - DEV Community 👩💻👨💻
In your setup, if you are using the node backend as an API to hydrate the frontend with data (not HTML or any markup), then you can assume the application to be JAMstack.