Not sure about UA, but QF often dump discounted Bus. and 1st on It'l routes. They very often have much tighter "rules" on them about re-routing, stops, and that kind of thing.

Still got identical points (thank goodness!) and if you were a fixed vacation traveller like me, and did not need instant flexibilty like a business traveller, they were great.

The same way a W or V on UA ain't nuthin like a Y or B, despite them all being nominally "coach" there will I am sure be differences between a F and an A in rules and conditions.