That's no kind of reason at all. There are movies that are only in pre-production listed at IMDB for God's sake. Be condescending though.
And what if my guess is correct and it IS the reason? I never said my guess was fact. I said "I imagine". And if my intention was to be condescending, I would not have used the sunglasses-smilie, mate. I worded it the way I did because the OP could have come to the same possible reason just as easily as I did.
The film is finished and ready for release now, thank-you-very-much.
Why not just ask the director about the reason? He's probably on social media if that's where the movie poster came from. The movie poster is where I saw the 2020 date.