Unlike other DSO's+ when a channel coupling is set to ground there's a perfectly flat baseline (i.e. no noise) - what's going on?

Unlike other DSO's+ when a channel coupling is set to ground there's a perfectly flat baseline (i.e. no noise) - what's going on?

When an input channel is set to ground, the scope simply draws a horizontal vector at the 0V position. Since the A/D isn't involved, the quantizing noise visible on most other DSO's isn't present.