the first official launch date they announced was april this year, when PS4 and XBox One S where the default consoles most people bought.
They say that 40% of the pre orders were for consoles. Since there were no next gen consoles in April, they would have lost 40% of their sales. Why doing that? You do not want to give up 40% of you sales, that would be stupid.
I assume they expected to get a "good enough" version out there and saw the amount of problems way too late in the project. And it is not like it was clear from the beginning that the game will suck on current gen. The PS4 seem to be in the 25+ fps range for like 95% of the time and for surprising long time even over 30, so getting it to quite stable 30fps is not unreasonable.
You see a lot of bugs but these bugs are not because they are on current gen consoles, they are here because of not enough testing...
I don't have the game at the moment, but I expect it to be pretty good after some patches and the next gen versions to be pretty impressive.