Well, that's a way to manage server-side logic, but your progressively-enhanced client-side logic (i.e. JS) still wasn't necessarily easy to debug, let alone being able to write unit tests for them.
True, don't remember doing much unit testing of JavaScript at that point. Even with BackboneJS and RequireJS, manual testing was pretty much the approach, trying to make it easy to repeat things with temporary dev UIs and such, that were commented out before deploying (FTPing). Probably not until AngularJS v1 came around, with Miško spreading the gospel of testing for frontend applications, together with Karma and PhantomJS, did it feel like the ecosystem started to pick up on testing.
> Astro find a very nice balance of having your server and client code in one codebase, being able to define which is which and not having to parse your data from whatever PHP is doing into your JavaScript code is a huge DX improvement.
the point is pretty much that you can do more JS for rich client-side interactions in a much more elegant way without throwing away the benefits of "back in the days" where that's not needed.