To put things into context, you have to understand how they define those measurements. Without knowing them, you are looking at something in isolation without understanding. I watched an old video of an Exit conference so I will try and help.
Reliability: Will it achieve death. Pn gave this a lower score because SN poisoning can be easily reversed. If you call for help or someone intervenes your attempt, ambulance is called. As soon as they put you on the ambulance they will give you 100% oxygen to breathe which is one of the protocols that saves you. Other methods if done right cannot be saved such as SA or a well placed gunshot to the head. The asterix comes from the fact the author admits they do not have a wide range of real cases to be able to score with certainty. I doubt anyone here writes to Exit about their failed or successful attempts. So in conclusion, reliabilty is low because you can be easily saved.
Speed: We will all have different metabolic rates and physical sturdiness. When I watched my mother die, they took away life support. Doctors said that she was not in pain and that she would pass within the hour. 6 hours later she died painlessly. You can predict if done properly, you will die, but nobody can give you a personalised schedule of how long it will take. This is one of the reasons I believe PN keeps upping the dosage to bring on death quicker.
With regards to the OP, it really does not take long to read the history of their posts and see a certain pattern forming. You can come to your own conclusion. They could be a scared kid who is wrestling with the anxiety of wanting to end their life but the action itself is scary. They could be lonely or just reaching out and trying to make contact and get attention. It has been long known that kids do something negative just to get attention. After all, attention is still attention. Or they could be someone looking to discredit this particular method. SN was the choice of one certain person who is now at peace and regularly comes up in mainstream media. If you look at a number of other peaceful methods here such as gun, hanging or CO poisoning, they can have the same risks. Yet they don't get anywhere near the same bombardment as SN. The OP has been given lots of help in this area to alleviate those concerns. However, regardless of the intent or where they are coming from, if you look at the posting history you cannot blame people for looking the vehicle (way questions are stated or making 'observations') that regardless of them saying this is their preferred way, they are doing an excellent job of unnecessarily concerning other members. They have also been given other alternatives that do not require regimen and have proven (if done correctly) to be equally successful.