To answer your question, I would say no, placebo/nocebo has no place in magic, and I'd argue that you are supposed to test your believed abilities repeatedly in such a way that it eliminates the possibility of the result being a placebo/nocebo or coincidence.
What if the person managed to cure someone else? Is the one being cured going through placebo?
If they can legitimately cure at least two more people with the same condition, using the same methods, then it wouldn't be a placebo (
of course that's if it's two more people consecutively, not two more successful cases with 10+ previous failed cases). If they only did it once, then it very well could be a placebo. They should have the desire to know the truth and experiment to find out.
One thing that always annoyed me in occult forums/communities, is that magic is usually spoken about as "one-offs". It's never treated as something that needs to be repeated in order to confirm your abilities. It's as if a lot of people don't believe that coincidences happen, or their egos are so huge that they'd rather attribute an outcome to their own being rather than to random chance.
"I did X ritual once and I got Y outcome"
I did a ritual to get a job and I got an interview for my dream job 2 months after and was hired
I did a ritual to curse someone and 1 year later they died in a freak accident
etc, etc, etc
The only question that comes to mind when I see stuff like this is - "Why would you even be satisfied with stopping there at a single result?"
I would never consider these things "magic" if I did it, I'd consider it me just getting lucky (coincidence), until I repeat those feats under similar conditions.
I think if you can actually perform a specific feat with magic, it should be as dependable as a lighter. There are conditions and actions required to make a lighter create a flame. It must have lighter fluid inside and you must press the button to cause the reactions that create the flame. You know that when the conditions and actions are met you will get a flame, and you can repeatedly test this and see the result yourself.
If a lighter could only create a flame for you once in your entire life of trying to use it, there would be no point in calling it a lighter. I look at magic the same way. If you can only make something happen once, like a fluke, like you got lucky, just call it a miracle, think of it as some unseen entity taking pity on you and sending a blessing your way. But there's no reason to call it magic if you can't repeat it over and over again.
I would not be surprised if one of the few lottery winners across history (that can't do magic) actually attempted some kind of occult ritual to win before they chose their numbers, and then they went on to spend the rest of their life thinking that they had magic powers. Even if they tried the ritual 100 more times and lost, they'd probably convince themselves that the stars and the moon were just aligned in a specific once in a lifetime way, which allowed their special abilities to work and win them the lottery.
People are much more concerned with feeling special (ego driven) than legitimately attaining abilities, so this way of magic will always be the norm, and that's why it's best to take most people's claims of abilities with a grain of salt.
Most people want to believe that they caused the miracles/perks they experience in life, and rarely will you find someone that will honestly tell you "I just got lucky, it had nothing to do with me".
I've only just begun my journey, and I may or may not get anywhere, but I know that I will be objective and judge myself by a simple strict rule:
If I believe I have exceptional abilities, then my life should reflect that belief, which means my life should also be exceptional. If that is not the case, I am delusional and lying to myself about my abilities.
It's that simple
If the average person tells me that they can read minds in real time, I'll ask them why they haven't retired already from their poker winnings.
I have yet to hear of a magic ability that couldn't be used in some way to very quickly become wealthy.