The counting for this is buggy+. The way the achievement is programmed, it should read "complete 20 (I think) director instructions in any season 1 episode across all playthroughs".
On my first playthrough, I missed a few, and the tracker was at 90%. On my second playthrough, during the tutorial (before I even pick out which actors I'm hiring) I get 2 director instructions and the achievement pops. I definitely got those in my first playthrough, so there's no need for unique director instructions.
tl;dr: Just keep replaying Season 1, any difficulty, and do whatever director instructions are easy. Don't fret over getting every last one. You'll probably get it during your second playthrough of Season 1.