I have found that to be true. I have also noticed that my first blooms don't show near if any fantasy but as they "mature" more fantasy shows up. I have also noticed that some blooms do show more fantasy markings and others little or none on the same plant. My Summer Carnival is a good example. Some are plain but others show random colored specks in the bloom. I am sure it has to do with the genes of the hybrid you have. Most of mine show better under cooler rather than warmer growing conditions. Not sure if this helps you or not because everyone's growing conditons are a little different.
One can only hope - it is good to know that as the plant matures, the Fantasy is more apt to return. I am hoping to regenerate this plant as I love the Fantasy on the blooms. I don't know the name of this one - it was unmarked in the nursery where I bought it.