Chris, I enjoyed reading your comment, it shows a deep study and knowledge of the art.
I can add that the late master Chan was really picky on rear hand's position when doing the tiger, but he slightly canged it over the last years of his life. As you can see in he pushes the rear hand quite forward, passing the front hand's elbow, let's say at 45 degrees with the center line. I have been taught this when I went to Hong Kong for the first time in 1977. Then he slightly changed the movement, sharpening the angle of the rear hand's elbow, so to have the rear hand on the side of the front hand's elbow. This way, the rear hand's forearm is presented to the opponent at a 90 degrees angle.
Another difference is the palm of the rear hand. Before it pointed at the opponent, then it pointed at the front hand's elbow.
We disscussed - well, it wasn't easy without a common language

but we managed to understand each other after many years of knoledge - this change with Cheung Yee Keung and we decided that master Chan just wanted to define a basic double fu chow, moving it from a double strike and push to a single strike and block. We never understood why. Maybe to go back to his master's roots (in his youth master Chan was an ambitious man and once became a sifu, he changed various parts of the art to suit his ideas and structure).
But it must be clear that this is just the basic, the form to be passed by and to be taught to the new students. The senior student must be aware that he needs to practice the form in all it's different variations of meanings. And that we did. Mi si-hing Kong Pui Wai always practiced the forms at least three times, first in the basic way, then in the "combat" variations. Seeing him training was always a great show!