Maybe I'm misinterpreting the science in a big way, but I don't think any of this is going to make any difference. If nobody is infected, it won't matter how long a scum is or how many people are in a ruck. The virus isn't going to germinate in a maul. If a player is infected, it won't matter either. If an infected person does make it on the field, that person will tackle, ruck maul and whatever else and as soon as they breath on someone, it won't matter how you stop that maul or how quickly you get the ball out of ruck.
Maybe I've got my head up my third point of contact on these laws. Feel free to let me know if you think so.
Just to be clear, I'm not saying we should go back to rugby and damn the consequences. Far from it. I just don't think these laws are going to have any impact on the chance of spreading the virus.