There is limited useful advice that could be given (which is also common sense). It’s unusual that the person says they have 8 papers and the supervisor thinks

There is limited useful advice that could be given (which is also common sense). It’s unusual that the person says they have 8 papers and the supervisor thinks he still doesn’t meet the requirements. If they have 8 meaningful papers in 4 years, no supervisor will be able to defend an argument to the graduate office for stopping the thesis (usually, they would want to promote such success in the department). The supervisor may think, the student is productive, maybe he could stay longer. But that’s far from an argument that the student doesn’t meet the requirements. There are regulations, checks and balances, various offices at universities that involve decision making and dispute resolution, etc. It’s not so arbitrary!