Specifically the 1926-27 saw a shift in roster composition with the teams you listed making the following adjustments. The following teams had RHS/LHS splits during the 1926-27 season Boston(Shore/Hitchman), Maroons(Dutton/Munro), Toronto, Canadiens, NYA had from before and did not change, Detroit(Laughlin/Duncan),Pittsburgh(McKinnon/L.Conacher). That left Ottawa which was cash poor but compensated with strong RHS centers - Nighbour, H.Smith, added the serviceable Al Shields within two years,NYR - very strong offensively but not top 3 defensively, until Heller and Seibert arrived. Seibert traded for another RHS Coulter then solidified Chicago. Chicago 1926-27 did not but corrected and added Cy Wentworth for the 1927-28 season.
So where does this leave your claim that a defenceman playing the opposite side was "rare"?
We've got 3 teams in 10 with exclusively LHS defencemen. That by itself is enough to make it not rare. But there's more.
We have the Bruins with Shore as RHS, then Sprague Cleghorn, Lionel Hitchman, Billy Stuart and Billy Coutu as LHS all in the lineup regularly. Coutu probably played some LW as he often did, but are you saying they rotated Cleghorn, Hitchman and Stuart in one position while Shore got no rest?
You say Dutton/Munro for the Maroons. But what about Reg Noble and Babe Donnelly, both LHS? Were the Maroons rotating Noble, Munro and Donnelly in one position while Dutton played the entire game?
You're off on the Pirates as well, since Conacher went to the Americans early in the season. Their two primary defencemen were Charlie Langlois and John McKinnon, both RHS. Tex White probably played some D for them as well, another RHS. Was Rodger Smith, their only LHS, on the ice the whole time for them?
So that's 6 of 10 teams that almost assuredly played
at least one man on the wrong side a great deal of the time. That's not rare. That's not even uncommon.
You imply that the lack of a RHS among Rangers defencemen was a weakness, and that they were "not top 3" defensively. This is a very selective bit of information, since they were in fact #4 in the league defensively, which is exactly where they ranked on offence as well, which you claim was their strength. Being #4 in goals scored (8% better than league average) means you're very strong, but being #4 in goals against (
18% better than league average) means you're weak? That seems incongruous to me.
Chicago did add a RHS the next season, and they went from dead last in GA to...dead last in GA. They continued to compensate by adding another RHS the next season (McKinnon). They were last in GA again.
There is no pattern here of teams trying to achieve balance between their blueliners.
The Rangers were in the league for six years before they had R/L balance on their blueline. In their first five years they played .559 hockey and won a Stanley Cup. Five years after first achieving this balance, they were heavy on RHS defencemen instead.
Moreover, they were coached by Lester Patrick. Are you telling me that
Lester Patrick didn't realize the vital importance of having balance among defencemen?
Lester Patrick? Or could it be instead that it was not in fact vitally important; it was a nice advantage if you can get it but a minor concern in the grand scheme of things; that having the best players you can get was far more important?