It's also really easy to screw it up, and many people do, some even after many attempts.
Not everybody is super diligent in researching the most effective methods, and some people may be genuine in their desire to die but are impulsive about it so may not choose the most effective method in their desperation to kill themselves now.
I'm not sure if we as outsiders are in any position to judge the sincerity of another's wish to die.
In individual cases, you may be right. But I think it's best to try to find the truth when talking about something so impactful as suicide as a general phenomenon.
And I am of course not denying that genuine attempts at suicide can fail. But that seems unlikely to be the key to understanding the massive gender disparities at hand here.
Unsatisfied with good suicide attempts going to waste, 4chan has found a method that's cheap, widely available, effective even with medical attention, and leaves the body completely unmarked.
So there are certainly gender differences, but it's not clear that it's a difference of intent.