If you accept the premise that the 1911 was designed and built for the cavalry, you also have to take into account that the saber was the primary weapon in a cavalry charge and the pistol was the secondary weapon while the Model 1911 was being developed. Until the Model 1912 holster, all holsters were right side, butt to the front for the pistol to be used in the left hand.
Also you have to forget the Hollywood scenes where the cops shuck out magazines right and left as if they were expendable equipment. Also, at what time would the trooper have attached the magazine to a lanyard. Did he stop, release the magazine, and attached it to a waiting lanyard, or did he wear enough lanyards already attched to the magazines? The magazine pockets were not designed to contain a magazine with a lanyard attached. One lanyard with a pistol and two magazines attached by means of extra snaps would have required some type of special holster to hold everything.
My idea on the lanyard loop on the magazine is that it was a good idea, but had no practical application. The military is slow to change, but by 1915 the lanyard loop on the magazine was considered useless and discontinued.