@puzzlezaddict - Bah you're right, I forgot about the Reroll Genetic Seed command. But, as you explained, that requires the baby to then actually be born after the Seed value is changed in order to note any difference. That isn't what I thought you were doing. With Play With Genetics, you can see the effects of the genetic reblend by "aging the sim up," one that is already born that is, within the PWG screen. That doesn't really age the sim up, it's just so that we can get a preview of what they will look like when they are older. And we can reroll as many times as we like until we get a combo that makes us happy.
What SP does is add player controlled parameters to the genetics settings and optionally invoke SP's Advanced Genetics system for more thorough and advanced blending as well as the ability to reach back to the grandparents for more genetic data. Without SP and Advanced Genetics EA standard is used, but the procedures are the same.