Yes, totally agree. There is no evidence out there to say when you 'should' start a weights programme. Patients need to achieve full ROM of the knee, have their strength assessed on something like an isokinetic machine and then get rehab'd accordingly. Their outcome is determined by what they can do functionally and you can formalise this with a scoring scale such as the IKDC.
There can't really be any arguement with this, if people are artificially delaying a patient from doing resistance work if they have full motion, no pain or swelling and a demonstrable weakness in the leg, then that makes no sense whatsoever.

Mark