It's true, you can use another file manager as your default in KDE, via the settings application. Don't take my word on this but it's something you can do as early as since the KDE4.x days, when Dolphin was starting out and people were used to Konqueror.
I understood flatiron to mean you can configure Dolphin to look and/or behave similarly to other file managers, not that you can literally swap it, even though you might be able to.
