In theory, the answers from question you quoted already answer your question. In a startup, it's a bad idea to have an ASP.NET developer who works only on the back end. In a large company, it can be suggested to have a dedicated developer for every task according to the skills of every person.
In practice, I never saw an ASP.NET developer working only on a back end, even on websites large enough. Also (but this is just my personal opinion), ASP.NET does a really bad job when it comes to separating work among people: it's difficult to have a dedicated C# developer and a dedicated HTML/CSS programmer; it's difficult to strictly separate a project into a front-end and a back-end.
Of course, things change when it comes to very large websites. Not only because you can't develop the whole website alone in a reasonable amount of time, but also because you'll lack the required skills or the knowledge of the overall project requirements.