Our twenty hole loading block is not required to make the easiest and nicest paper cartridges in the world. The basic set is just fine, but you do have to make one cartridge at a time.
There is no problem with one at a time, except that you do lose time switching from one task to the next for every cartridge. If you are loading for competition regularly, the loading block is going to save you some time, or at least allow you to produce more cartridges in the time you are able to set aside.
The one exception is if you are loading roundballs. With roundballs, you have to kind of roll the ball in glue, then place it in the open cartridge mouth, removing your finger from the ball carefully and moving on to the next.
This can be a challenge with grabbing the next paper, as the fingers tend to get a bit sticky.
The loading block will allow you to make 20 papers, then do the powder, then the balls, with your nasty sticky fingers, before having to wash them.