A lot of developers have made or just perceive very strong silos between frontend and backend today. Any coordination that needs to happen between frontend and backend is potentially a communication challenge.

It seems like a lot more work because you have to keep the backend and frontend in closer sync. The backend has to be aware of and able to store every sub-form in the full process (which sounds like a "wizard form" with a multiple sub-forms to get through the full "form" process), not just accept a "finished" or "complete" submission. If a sub-form needs a change the backend, the backend's storage, and the frontend all need to change. The backend and frontend have to agree on validation logic for each small piece of the form. The backend and the frontend need to both validate every small piece of the form, and maybe can't share that validation logic (depending on what language the backend is written in), especially if one of the goals is to do as much of the frontend validation as possible with Browser native validation tools (`<input required` and `<input type="email"` and so forth) so that you get the most benefits of progressive enhancement.

The original ways of making websites were "full stack" and from a full stack perspective it shouldn't seem that hard to have a coordinated frontend and backend, especially when a progressive enhancement approach likely means a smaller more agile frontend, but current siloed world where frontend and backend are different teams with different goals and alignment makes that seem like way too much work.