Imagine getting a can of purple paint and trying to figure out exactly how much red and blue dye was used to make that exact purple. Now imagine doing that every few lines of code in a code base of say 10k lines. That’s basically how decompilation goes. It’s extremely hard and even if you’re able to figure it all out, it’s still impossible to ever know what was actually originally written.

What you’re describing though does have done truth to it. There was a time when you could get a program from a magazine, type it all in to your commodore 64, and then it would run a pacman clone. These, line python today, are not compiled. So to have the program means to have the code too.