It's funny how we so strongly disagree further down in the comments, but I 100% agree with you here.
0,38g being largely fine for health is... I mean, if I had to bet, I'd put my money on it probably being true, but it's anything but guaranteed. There was a private project to test this, the Mars Gravity Biosatellite, but it ran out of funding; I'm not aware of any similar experiments that have been conducted. There've been a variety of attempts to simulate various gravity on Earth, such as having people lie on tilted beds or hanging them from cranes at an angle or whatnot, but they all have obvious weaknesses.
There's not just the question of adults who visit from Earth, but also children who grow up on 0,38g, and what impact that would have to their physiology.