Yes and no.
Booking classes represent the inventory. So to stick with your United example: On a domestic flight, United would split the actual Economy cabin into 15 virtual ones. Each of those would get a different size based on whatever level of demand United predicts for a given day. Then each of these gets sold via different fares (hence them occasionally being called “fare buckets”). Buckets for lower fares would typically be smaller (they sell out faster) and they would also be “nested” within the higher ones, so if more capacity of a higher fare is sold, it’ll cut into the inventory of lower fares. On top of that, the airline’s revenue management system would decide when certain booking classes are opened and closed.
But at the end of the day, it’s the fares that determine the price and the rules. In my LH example above, all 4 fares are available for booking class Z. To illustrate, I just had another look at a flight from FRA to DEN (same date, same search result, just different connections):
Booking class Z:
Booking class D:
Booking class C:
So in LH’s terms, there are 3 general Business fare types…Basic, Basic Plus and Flex. And the latter will always be more expensive than the former. But the overall price level is determined by what inventory is still available/open for booking. Technically, my example amounts to a total of 9 fares. Three for each booking code.
With a pattern like Unite’s (or any network carrier’s) in place, where certain codes are always used for high/full/discounted fares, it also makes sense to use those as the basis for points/miles in frequent flyer programs. And yes…those would definitely be a separate roadmap item 