Seed combos - and seeds in general - take a good amount of time. They are almost "games within the game" with their own set of rules and problems. I can think of one that shall not be named that has been particularly pesky to get "right".
I think it would be fair to say that this particular section of the update has caused some portion of the length of the time taken... but we are too far down the road now. Not every seed combo is a "secret/special" combo to be clear - so it isn't 128 special seed combos that we are trying to manage. However, each one needs special care - again, like a game within a game.
We have debated such, but as
@J Bame noted, this would likely create more confusion than helping things. Game dev is not a linear process... just for one.