Under-powered also means that the minimum detectable effect is high (that's why it is harder to get a "significant" result). Which means that it is more likely

Under-powered also means that the minimum detectable effect is high (that's why it is harder to get a "significant" result). Which means that it is more likely that if you will find an effect only if you are overestimating the real effect. The real effect might not even be detectable!