If Adam is a warlock, he doesn't display it in the quasi spin-off Tabitha series, featuring an adult Tabitha and Adam Stephens. However, in the animated cartoon special Tabitha and Adam and the Clown Family, he definitely shows that he inherited Samantha's powers, albeit grudgingly.
It is never fully disclosed if Adam is a true warlock or his powers are the result of grand-daddy Maurice's refusal to have a mortal grandson.
This episode completed filming on August 5, 1971. A rerun of this episode aired on July 1, 1972, the last time that Bewitched was ever broadcast on ABC in primetime.