The current system already has surveillance. And it's very likely that some hidden score system is already in place (because surveillance is basically useless without some kind of data-analaysis/filtering tools, which boils down to giving scores to people...) So with the current system, you may be denied government jobs or access to some services based on this hidden scoring system already in place. You will be denied but without knowing why, with no clues on how to fix this.
With an explicit social score, contrary to the current system, you see your score going down whenever you do something that does not please the gov. You also get an explicit score increase or (whatever reward) if you manage to change your behavior to please the gov. This makes it possible to understand why your score might go down and to game the system to bring your score back to normal. Gaming the system and understanding how to regain access to denied services is not possible with the (probably) currently implemented hidden scores.
Of course, I am fully against this type of surveillance and thankful of not living in such country. But the idea the the new, more explicit social credit scores will be worse than the current system can be challenged.