If my search backward through Watchtower pages is correct, the May 15, 1944 issue was the doctrinal turning point of the disfellowshipping procedure.
Prior to that, a behavioral problem of some member was placed before the company (today's congregation) and it was decided by the democratic process. I don't know whether it was a show of hands, an audible voicing of ayes and nays, a paper ballot, or what. As you can imagine it must've been extremely embarrasing for the accused. It probably wasn't much fun for anyone in the audience -- kind of like throwing stones in ancient days. Okay -- perhaps some folks thrived on that kind of thing.
The following brief excerpt is is from that issue, page 151:
...This brings up the questions: Is there anything in the Bible as to disfellowshiping brethren and as to a congregation’s taking a vote to have this done? ... In times past those words of the Lord have been interpreted to this effect: That, where one member of the church sins against another, the matter is, after due process, to be brought before a whole congregation. There it should be discussed and argued out. Then a vote should be taken by stretching forth the hand of each member of the congregation in a democratic-voting manner. Thus the congregation must indicate its determination of what should be done with the one found guilty.
Putting such a meaning into our Lord’s words, however, has served to cause more controversy and disruption among congregations in times past than almost any other thing.
Following that, it was argued that certain ones in roles of authority within the local congregation would be better suited to performing the dastardly task.
What surprises me is that the change was done on Knorr's watch and not Rutherford's. Recall that Rutherford had already passed away some two years earlier on January 8, 1942.
Len