I understand that the signature only signifies that 'an hour's instructional flight was undertaken'
Nowt more and nowt less. So if that is true you can not not decline to sign it.
May be best to return to base before the hour is up! (especially if it is that bad!)
Not surprised that some of the worst experiences are with people who have been able to extricate themselves from any monitoring/guidance for years by virtue of having their own machine.
Another personal observation is that the more vociferious the pilot is about these requirements, the more they are in need of a bit of 'guidance'
FD