It looks like that article in question is actually a compilation of Siegel quotes that I stitched together from various sources, although it's possible that all of the quotes are from that 1983 Nemo #2 interview as you state. I just haven't managed to sift all of them out yet.
Every paragraph but the last one appears in the NEMO interview, though some are worded slightly differently -- possibly editing for clarity, possibly Siegel telling the same stories over and over, so his wording started to get almost identical with each iteration. For instance:
Interview:
Well, as a science-fiction fan, I knew of the various themes in the field. The superman theme has been one of the themes ever since Samson and Hercules; and I just sat down and wrote a story of that type—only in this story, the Superman was a villain.
Edited Essay:
As a science fiction fan, I have long been very familiar with the various themes in the field. The superman theme has been one of them ever since Samson and Hercules. I just sat down and wrote a story of that type - only in this first story, the Superman was a villain.
Interview:
It occurred to me: What if I was real terrific? What if I had something special going for me, like jumping over buildings or throwing cars around or something like that?
Essay:
So it occured to me: What if I was really terrific? What if I had something special going for me, like jumping over buildings or throwing cars around or something like that?
Interview:
Carter was able to leap great distances because the planet Mars was smaller that the planet Earth; and he had great strength.
Essay:
Edgar Rice Burroughs' John Carter was able to leap great distances while on Mars because the planet was smaller than Earth, and so he had great strength.
If the last line appears somewhere in the interview, I didn't spot it. But for the most part, that text, in substantially-similar form, appears in NEMO in that order -- it's edited down, but not moved around.
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