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No, it's true from what I've seen. I've seen numerous diaper tumblers, comics, characters/series with incontinent characters and never once has it not been someone with the fetish making fetish content.
I've seen enough that I feel very confident in saying that what you have is part of that rare, exceptional 5%, assuming that person doesn't have the fetish at all.
Keep in mind I said 95%, not 100%. Maybe there's a small exceptional group out there but I don't think I've ever seen it. I don't think anyone in diapers would want the world to know.
I've also seen plenty of examples of people who made themselves incontinent because of the fetish.