I know I am late to the party, but I have seen this argument many times and it is wrong.
In order to hit anybody in the face with a wrench, you need to find their present location, physically send out physical thugs with a physical wrench and do the face hitting. That is a lot of effort and it doesn't scale well. Plus, when all hell breaks loose, there is the option of resistance via second amendment or flight.
When everybody's everything is a mere number in a database somewhere, things like 'freeze assets of everyone present at location X at time Y' (political rally or whatever) can be done in an automated fashion with basically zero effort required and zero order scaling. And there is no straightforward way of resistance or evasion.
that is a significant difference.
Another aspect of 'cashless' that I never see mentioned is the institution of negative interest imposed on deposits. When there is no cash the government can basically force you to spend your money.