You're correct, and I'm generally in favor of the right to die.
I watched a documentary where they interviewed a bunch of people who attempted suicide and talked to them about the entire experience and mental state. Out of the maybe ten that they interviewed, only one said that he wished it had worked. That doesn't mean it's only 10% though... they didn't get to interview the ones that succeeded.
No, it isn’t. People who have attempted suicide are often very closely monitored by family/caregivers/medical professionals for whether they are going to attempt again, for years, and can be subject to significant constraints if they give any indications that they are thinking that way.
Sure, but the comment of was about the illegality of suicide and the resulting jeopardy causing people who attempted suicide to say they didn't wish it had worked on a documentary about suicide (and presumably skewing the "stats").
I don't think that's the same as what you're describing.
With suicide being illegal in most jurisdictions, not everyone interviewed may have been honest in relating their feelings. If you have suicidal ideations, telling others about them can have severely negative consequences. Saying “I wish it had worked” would likely create ongoing jeopardy.