Technoprat;
In my experience engineers love to come for a post maintainence test flight. They just don't have time. I worked for the same company as Training Centre and sometimes we could tell the supervisor we wanted the boys along to discuss any problems as they occured, rather than trying to describe them later.
I think you will find that Flap 5 is making a very tongue in cheek comment. I have had an engineer say to me "fly in that? after what we've just done to it? No chance matey!" The truth was he had 2 more aircraft he was supervising at the time and couldn't leave, but the banter was fun.