I doubt that Yeon Heyop is Jintae. It's possible that the real Jintae has rewritten Yeon's memory and is pulling the strings behind the scenes, just like Rohee.
And I agree with the comments below: Director Yoon is Jintae.
Because there's something off with his behaviour..
Toss a pebble at my window when we get back to the plot, and hit me with a boulder if Cliff shows his face