When the foundations were laid for the stadium I seem to remember being told, on a conducted tour, that the reason the stands were so far from the pitch was that future development could lower the pitch and put 6 more rows of seats in front of the stands.
The general idea was that the initial 4 sided ground would hold around 15,300, filling in the corners would take it to around 19,000 and six more rows at the front would make it around 23,500 (with the crowd closer to the pitch). Added to that would be the Executive lounge at the top and back of the East Stand and a supporters club area under that at the back of the East Stand. There would also be development (e.g. fitness centre) under the West Stand (yet to be built).
This was all before FK.