In a general aviation aircraft (28V DC) once the engine is running and the alternator brought on line it takes over the battery load (literally - outputs a higher voltage) and provides all of the power for aircraft systems while charging the battery too. So I would say the folks that posit no 2 are better informed on this.
In larger aircraft, generators are used to supply AC current to a majority of systems, while TR units charge the main battery and supply power to all of the DC systems.
Oh, and MG, I thought you knew all about this stuff
