Damn you for making me read the entire FA
They did do a study that contradicts earlier experiments:
A person's natural circadian rhythm averages about 24 hours and six minutes for women, and 24 hours and 12 minutes for men. It varies for each individual, but doesn't stray very far from 24 hours. At about the time Pathfinder landed, Czeisler and his team began conducting studies at the hospital's special laboratory that shielded study subjects from all outside influences. With their test subjects in isolation, they simulated the Martian sol to see how the test subjects adjusted to the longer day. "What we learned was none of the people adapted their circadian rhythms to the Martian day," Czeisler said.
So either earlier studies were off, or Czeisler's experiment was wrong (having e.g. the HVAC on a 24-h cycle, or background noise etc.).