A pretty good grasp on the fundamentals, there, Bob.....
While DOH (used as shorthand for longevity) is determinate in some areas - what step of the payscale a pilot is on, how much vacation a pilot gets, boarding for non-rev travel if that's the system used, etc - none of that is affected by this award.
This award only affects bidding for equipment, bases, seat, and nothing else. There, DOH doesn't mean squat across airlines. For example, take a UA, a HP, and a US (East) pilot with all three having 15 years of longevity. The first may be a 767 captain, the second a 737 captain, and the third is furloughed. Does their longevity get them all the same result - the same seniority? Obviously not.
That's the problem with mergers - you take pilots who have different seniority for their DOH and force them onto one seniority list.
Doing it by the "one size fits all" method of DOH gives the pilot how didn't have enough seniority to hold a job seniority equal to the pilot who had enough seniority to be a widebody captain (or conversely takes seniority away from the pilot who held a widebody job so that he's equal to the guy who couldn't hold a job).
Some insist that "robbing Peter to pay Paul" is the only fair way while others insist it's fundamentally unfair. And that's what all the fuss is about.
Jim