Because buying the "Easy & recommended spring" for a stock head is a insane choice since he has Edelbrock heads with a taller installed height and 1.6 rockers.
The current valve springs would show the engines power curve nose over pretty good instead of hanging on longer.
I myself would look deeper into the catolog for a different spring than the ones listed just to be sure there isn't a better one. Even IF the engine was using a 1.5 rocker, I'd still look. There is more than just a few pounds difference NOT to worry about and call good enough to just get away with.
It just makes good sense.