yes ... the only caveat I will offer about these J seats is that you have to be a contortionist to get out of the window seat if the passenger in the aisle seat has it in the full (or nearly) flat position

DL has a number of ATL<-->SEA flights that are continuations of international trips: these will display the premium booking inventory codes, but unless there's a "flat bed" icon in the flight info section you're almost certainly going to get 20 standard domestic F seats on a 757 or a 737-900 ... that said, typically they run a 767-300 on an early morning (~0830) westbound and a mid-morning (~1045) eastbound trip, and there are usually 36 flat-beds on those jets (even though it will be standard domestic F service)