I have no experience in checking control columns on smaller turboprops, but on the Boeings it is done in some way like this; first one of the two control columns is blocked in neutral, with trims at zero. Then a specified amount of force is exercised on the free column; eg 2 lbs on ailerons from what I recall. This should give a certain degree of deflection on the free column, whose limits are specified in AMM. If the degree of deflection is too high, that same AMM gives you a list of items to check for wear and play - mostly bushings and rod connections. If rivets are loose they should be in alert phase, certainly not deferring it till end of the year. They also should be aware on which items cannot be repaired with oversized bolts or rivets, chapter 27 is too important.
This is Boeing of course, but the AMM for smaller turboprops must have similar limits, your engineering dept sounds unprofessional from what I read.