It would not be reasonable to expect that each developer has the game already completed before being accepted into the developer program, especially since you can’t make sure performance and features work on the console without being part of the dev program.
And honestly, they’ve got plenty of very ■■■■■■ games on PS4 so the barrier can’t be all that high. The limitation is mainly just to avoid people that aren’t serious about releasing a game, if you’re a hobbyist and you’re just curious about messing with developing for PS4 then you’re not likely to get accepted into the program.