A technical writer is basically a business analyst and writer packaged as one. There are many reasons that this statement is true. To put it simply, just think about what a freelance technical writer does day to day. They take on a specific type of technical writing project and have to analyse discrete and systemic aspects of a business, their product, etc., and then they have to do it again with a completely different client.
It’s fair to say that technical writing is one of the toughest tasks out there. So the typical business analyst may struggle with creating this type of documentation. A general writer is also not going to have the level of business experience and analytic understanding required to create completely accurate content.