If they were captive-bred, they've probably been raised in a tank full of other clownfish and never really encountered a serious threat of any kind. Wild-born clownfish, on the other hand, would likely have learned to live in anemones to avoid predators.
That's not to say that captive-bred clowns won't eventually learn to live in an anemone...it could take months to find out. This all depends on the health of your anemone though - don't expect clowns to make a dying anemone their home.
Kinda funny, last night bout 4am, i had the LEDs shining on the tank a lil bit, caught the Clarkii basking in the LT anenome, first time ever... I was quite excited.