I learned this myth you brought up in CO board but I couldn't take it seriously because there are many NW elites ever upgraded onboard on NW flights including myself.

I was upgraded on board once on MEM to LAX and once on LAX to MSP.

I ever witnessed CO gate agent bypass a standby member for upgrade at gate at CMH once. (His friends was shouting at the gate agent saying the standby guy is already onboard when he heard his friend's name, but the agent still skipped him and gave the upgrade to other guy with a new boarding pass at gate)
However, I wouldn't generalize this coincedence as a policy of CO.
I deem this lack of training or laziness. There are always some bad apples.

For what you experienced at DTW, you should have written down the whole thing and filed a complaint to NW.

[This message has been edited by VinceLee (edited 06-09-2001).]