What would you do if they refused this offer, got their rating revalidated and a few days later hurt themselves or god forbid killed themself and others with them because they made mistakes that you had picked up, tried to rectify but failed to do so and then gave up and signed the form and logbook anway?
Tough luck...they are revalidating by "EXPERIENCE" not by test. If they have survived 12 hours on their own, and managed to get revalidated then obviously the CAA thinks this is good enough....
If on the other hand they are revalidating by TEST with an FE then fair enough.