Features change on implementation. Some times the original idea doesn't work out, sometimes a feature that some people say they don't like works far better than expected.
Ideas have been asked for and debated by the community at great length and a long list, that has been cut down into a list of features that the game makers want to do is made.
These features can & will change depending on how well the testing of them works and how much time there is. Sometime unliked features appear at the discrtion of the programmer because it the only one that worked at the time and/or the other ideas didn't work out.
Provided the result sticks mostly to the original spec (and works) then most bespoke programming is accepted, or it can be changed in a patch later so the software can be produced on time. (cough M$ Windows XP, Vista cough)
Most people will know of the various things that the programmers of Vista decided not to implement due to time contraints, some of which have resulted in other ideas, that were less liked being used. (I personally doubt WinFS will ever get anywhere in the next 10 years even if it was going to be a better filesystem, which funily was going to work like the current *nix journalling filesystems. But time constraints resulted in the next best thing called NTFS (cough yuk cough) being used again)