Based on the weekend operation, yes.So you agree that 20 units are superfluous? Or some lesser number?
In terms of weekdays, isn't the point that multiple peak extra trains don't run any more, so there is scope in the fleet to run more 10-coach trains even without 20 units? For example, there aren't trains every ten minutes from Liverpool Street to Southend, and no need to run as many fast services to Cambridge.
The balancing act is where services are tight as a single 720.