most likely was the fact that the muzzlebrakes were not a big deal, all too many folks ( shooters that I knew and shot with) noticed ,little of no difference, were a pain to clean, some guys did better taping a roll of dimes to the underside of the barrel to keep it "muzzle down"....no large movement for slaes ,so simple done away with...if it was not a "big deal" then the various writers did not make much of writing about, few if any books "cover it all", the various writers ,write what they know about and with what information they may have at hand, like the words of our friend Jeff Munnell, "write something else your self and prove me wrong..."
yes, they tried again with the tapered 5 1/4 inch barrels, see them in blued as well as stainless in Mark IIs , as well as with the P series polymer frames (22/45) I like them , nice balance and feel....they just did NOT sell that great, and cost more to make in the scheme of things.............