They didn't say "reality must be wrong". They said that their initial hypothesis (that significant changes would be observed after 21 days) is probably wrong, so they implicitly proposed a second hypothesis (that significant changes occur after e.g. a few months).
None of this is remotely contemptible.
Pretend you're an immortal alien conducting a study with the hypothesis, "humans are mortal". You observe that your subjects do not die after 21 days. Do you conclude that humans are immortal? (I hope not. It's much better to conclude that humans don't usually die after 21 days in this particular instance of extraterrestrial captivity.)
None of this is remotely contemptible.
Pretend you're an immortal alien conducting a study with the hypothesis, "humans are mortal". You observe that your subjects do not die after 21 days. Do you conclude that humans are immortal? (I hope not. It's much better to conclude that humans don't usually die after 21 days in this particular instance of extraterrestrial captivity.)