Brad, I totally agree with you and Jeremy that the 10 mm 044 and D chamber 046s are just "indicators" of saws with better factory port timing, and that port timing is what makes the difference.
However, I thought only the early 046s had the D chamber, but I could be wrong. My information is totally from what others have posted on this website.
Have you seen D chambers on 460s that appear to be factory original?
Any one else with information on this?