I don't know how the system works so this is just a shot in the dark but I assume that it has to do with the time it takes to pass a bill. A tabled bill can be quickly brought to vote where as if they had to start the process over again as a new bill it would take longer and give the people time to react.All bills are possible to be re-instated in the future.
Is the demand that Hong Kong's basic law be amendment to prohibit the passing of any extradition bill with he mainland?
Is that even a desired outcome?
At some point you're gonna have to sort that shit out.
But, whether that assumption is correct or not, there is still the core issue of the optics behind what they did and how they did it. Saying it's tabled vs saying it has been removed is a bad look, even if the result is effectively the same. The government refused to look weak and they keep digging down.