There's definitely at least some truth to this. And even when working on both frontend and backend (on a small team), I find it useful to have a clear separatio

There's definitely at least some truth to this. And even when working on both frontend and backend (on a small team), I find it useful to have a clear separation between client-side code and server-side code, with a well-defined boundary between them. This might be shaped by my experience with ASP.NET and .aspx templates, though; I struggled to understand when and how the client-side code would call the backend to send input or get updated data.