Actually, the same thing is true for HTML legacy color parsing too, but the only difference there is a few lines of code. I think it is these lines that was added (from http://mxr.mozilla.org/classic/source/lib/layout/layimage.c#...):

  if (bytes_per_val > 4)
  {
        bytes_per_val = 4;
  }

Table parsing is nowhere near that similar. It's almost certain IE's algorithm is largely different — it just obtains similar results to NN's in most cases.