No they couldn't. You can't create software you don't understand because you wouldn't even know what to type into the IDE in the first place. I don't understand claims like these, how exactly are people especially individuals producing more code than they could understand? Even at a huge corporation one might not understand all the code but surely they understand the part they're modifying because otherwise they wouldnt know how to modify it.
Yes, it’s possible for a person to create software he doesn’t understand himself. In the old days this was pasting from Stack Overflow and changing things until it worked.
In the old days even if I knew how the software worked when I wrote it, I’d have no idea how it worked when I looked at it weeks later.
It’s also easy to modify software without knowing how it works. This produces modifications that hopefully appear to work, but that break other things, sometimes unknown things.