i would not be the final authority on this however
using a SE source would only be equal to using a balanced source if the amplifier is a perfect SE->Diff converter. for a low feedback design like Gilmore's this will require great parts matching and thermal control
also, the typical source adds extra op-amps to convert balanced to single ended. so you are adding an extra op-amp stage that is not needed
but still, what luvdunhill said