It might not be all that important to the actual story of the film but it adds some potential flavor to the world.
I think it's that it's a Superman element in a Batman movie and what it might mean for the universe of said film. Especially for characters who, generally, share the same universe.Why is everyone so ready to jump on this as some big Superman confirmation? There's no sense of "Could be nothing/an easter egg" here.
Maybe we're just desperate for another Superman and need to hold on to any hope?