Yes, all very strange. I believe in a competency/experience based assessment. It is possible due to seniority in my company that a pilot will not actually approach and land at minimum conditions for 15-20 years when finally a number will come up for command assessment. It is indeed a trial by fire for these people and the upgrade is feared by many. The other stupid part of it is the situation where many new hires are extremely experienced(including yours truly) and have been jet captains with 10 or 15 thousand hours plus.
If a pilot satisfactorily demonstrates in training the ability to operate to minimums/maximums then the PF/PNF role should be interchangeable. If a pilot cannot demonstrate this then upgrades should be refused. It is a very silly situation to find this out after 20 years with the company, and really should be discovered in the probation years.