This is interesting historically, but as the article points out, none of this stuff really works on modern RGB displays that use integer intensities rather than 1-bit values.
You can think of Porter Duff compositing as an upprojection of bitblt to
multidimensional, continuous space.
It's the fact that there are three components that causes the problem, not integers per se, since even one bit RGB (for a total of 8 colours) would not allow xor tricks.