Shri, your list of training, along with your experience climbing in Iceland puts you way ahead.
That paragraph you quoted was posted by me, but written by Bob R, a mountaineer and Search-And-Rescue team member. It was written years ago (before Facebook, etc), when the Whitney Message Board was visited by many novices who would post that they just wanted to hit Mt Whitney in winter -- I think maybe their primary reason was that there is no permit quota.
So it was written to forewarn such people that they needed some winter mountaineering experience. You have some experience already, and are planning to get more. Keep up with your research, and I think you will be prepared to have a good experience.
