A similar problem is when one person says "I am unable to do X" and another person says "I find it extremely difficult to do X, but with lot of suffering I somehow manage to do it anyway", you never know whether the second person had more willpower or better strategy or maybe more supportive environment, or simply their symptoms were less strong.
No matter how you decide to see it, it ends up blaming someone. If you decide the problem was the same, then you can blame the first person for not trying hard enough: "see, the second person had the same problem, but they didn't give up, they thought positively, tried harder and overcame the problem, why can't you do the same?" But if you decide that the problem was not the same, then you can blame the second person: "see, you were able to do it after all, which shows that you were only pretending to have the problem, unlike the people who actually suffer from it and cannot do anything about it!"
Of course in real life many problems are on a scale; for different people doing X may be "easy", "difficult but possible", or "impossible". But many people want to round this to "yes" or "no". -- "Either you have depression or you don't. Either it is possible to do X when you are depressed, or it is not. If it is possible, then people who claim they are too depressed to do X are just lying. If it is not possible, then people who manage to do X with great effort were lying about being depressed." -- It works similarly for topics other than depression, too.
No matter how you decide to see it, it ends up blaming someone. If you decide the problem was the same, then you can blame the first person for not trying hard enough: "see, the second person had the same problem, but they didn't give up, they thought positively, tried harder and overcame the problem, why can't you do the same?" But if you decide that the problem was not the same, then you can blame the second person: "see, you were able to do it after all, which shows that you were only pretending to have the problem, unlike the people who actually suffer from it and cannot do anything about it!"
Of course in real life many problems are on a scale; for different people doing X may be "easy", "difficult but possible", or "impossible". But many people want to round this to "yes" or "no". -- "Either you have depression or you don't. Either it is possible to do X when you are depressed, or it is not. If it is possible, then people who claim they are too depressed to do X are just lying. If it is not possible, then people who manage to do X with great effort were lying about being depressed." -- It works similarly for topics other than depression, too.