LProuse:
Well, that's not quite true. I don't want to rehash all I wrote quite some while back so go back and take a look at the referral link if you're interested.
Let me be more specific. I was a member of the TWA MEC in the mid-1980s. What I stated was the absolute policy at TWA. At MEC meetings we were advised by the experts that TWA's policy was in compliance with FAA requirements and industry standards.
We were never advised that the on-duty apprehension requirements were more relaxed, apparently significantly more relaxed, at some other carriers. Nor, do I recall it being mentioned by anyone in an ad hoc manner.
We had two or three cases of termination for showing up in circumstances quite similar to the case of this thread. Those terminations were sustained at the five person board. I was not privy to the record of those cases but if ALPA legal argued the more permissive policies at some other carriers, it did not carry the day. It could be, though, that a retirement deal was cut in the late stages of those cases, and we just thought termination had been sustained.