Steam 710 Weak Low Speed Braking - Bug Or Intentional?

Recently I've been wondering why the brakes on the 710 seem to be quite weak at low speeds for a modern commuter train. I can't tell if this is just the nature of the Aventra brakes and it's an accurate depiction of real life or whether this is unintended. This question doesn't appear to have been asked here before, so does anyone have an answer?