Note that Flight 2368 ATL-SEA is currently being flown by an 763ER which has lie-flat seats. The other 763 flights on this route are standard domestic FC config 763's. As has been noted here many times, other than the JFK trans-con routes, any domestic routes with a "business" designation are simply continuation flights of international flights. They do not guarantee any particular level of seating or service. These are readily identified as they typically have a 3 digit or less flight number. Note that flight 2368 BE seats are not sold as J fare classes because it is not a continuation of an international flight. And, of course, there's no guarantee it will remain a 763ER. It's almost certainly currently being flown with that equipment for positioning reasons for an international flight out of SEA.
Similarly, DL773 starts ATL-PDX then PDX-NRT. Nice domestic lie-flat 763ER from Atlanta to Portland (at least the one I was on last week was).