OverDone

The truth hurts sometimes....

Yeah, he explains it in the novel. I can't remember what I thought when I originally commented. It is likely just a bad translation or word choice at that point. I believe the author meant that he wasn't unhealthy or suffering from things like organ stress or nerve problems which would be expected for rapid growth. If I remember correctly, the MC eventually stops and grows at a normal or slow rate and gains control of his ability making any body problems a non-issue. Besides, people have to suspend disbelief for a lot of fantasy works because normal people in those worlds are just less observant or caring about strange things.

In that case, it is even worse. He is growing way too fast. Also, Robert Wadlow's situation is an abnormality that no doctor would say was fine. In fact, you already stated the abnormality the doctors diagnosed him with (excessive growth hormone). Yes, it is entirely unrealistic to think all these normal non-jjk doctors would say he was completely fine especially if they use Robert Wadlow as an example seeing as he also had many other health problems caused by his excessive growth. They might admit to not finding any cause, but would definitely state something was off and ask him to be routinely tested.

Ahhhhh he chose to write historical fiction instead of history without any good fiction plots.... what an idiot.

The problem with that is that it is common to them. Some might really enjoy the history. Others have heard the stories so many times they don't care to read about it as well. Also, with it being real ninjas everyone will just think it is embellished propaganda.

Nah, it's crazy. His is magnet release and he uses that magnet release to magnetize the sand particles. Other shinobi manipulate sand with earth release, but they only do one time attacks (Earth Release: Sand Dance) not move waves of sand with a flick of a finger.

He is giving them hope when there is none and sending them in the wrong direction. No, fish merchant is going to just hire a bunch of homeless people even if they do show up with their own cleavers.

Oh right! Rasa has red hair

Save Baki!!! He has to kill Hayate Gekko in the future. If he doesn't, Hayate will keep spreading the plague.

Gaara's makes no sense. The 3rd, 4th, and 5th kazekage all had magnet release. Rasa had gold which isn't magnetic. Gaara had sand and by the color we see it is silica also not magnetic. The 3rd used iron the only magnetic one and since you can get magnetite (black iron) from sand it makes sense in appearance as well. The way it is explained in anime and that they forcibly magnetize the substance they control and Rasa used gold because it weighs more and can suppress regular sand manipulation.