IniSky
You had to sign logbooks to verify you had observed the logbook contained evidence of sufficient hours, 5 in 13 months.
You now have to sign saying you have flown one hour with the pilot.
Both signatures are recording a statement of fact, and under the rules is there really a legal problem.
Your question about refusal to sign should perhaps be amended to has anyone had any serious arguement with a pilot after suggesting they carry out more refresher instruction.
A supplementary question would be how many times has it been necessary to recommend refresher instruction.