I don’t think there is any intentional bait and switch.

The issue is what is sold needs to be consistent from a fare bucket and inventory perspective, especially on flights offered as codeshare and interline. I expect the planned aircraft config for a given flight is accurate when inventory is loaded.

The problem is that due to maintenance or other operational issues, that specific aircraft config isn’t necessarily available at time of operational finalization that typically starts at 72 hours before flight and can often have several different tails reassigned over that 72 hour period. The inventory from a sales perspective can’t be synced back easily when operational changes take place.

Airlines that don’t do codeshare or interline and use a single sales and operational system with a central database, as opposed to flow-based systems necessitated by codeshare, have the capability for inventory reflecting aircraft assigned in real-time.