The below from Dec 1951 Hoof and there was still some racing remaining for that year.
Please note:Harness yearly stats were tabulated on a DEC 1 thru NOV 30 year until the late 60's.The Christmas issues of racing mags had the final year's stats.
Starts in December were shown in the race programs as being the subsequent year.About 1969 there was a "13 month" year.
Only problem with your theory is that these 1949-50-51 HB issues were mailed and postmarked 7-10 days before the end of the previous month. (Thus this Dec 1951 was mailed before the end of November).
Additionally, if the HB'e were mailed prior to the end of the previous month?
When were the articles and stats actualy complied?
Where as a long published magazine like Harness Horse or HF&W, I'd say that the periodicals had an established method which allowed editing to provide the most recent stats, however the USTA in 1949 moved their entire staff into that little three-story house in Columbus, and then began hiring many non-horsey people from the Columbus area to fill clerical positions.
The issues were vibrant with errors, and the editorial direction of the magazine seem to take new turns at every issue.
I don't believe there was any stability in the Columbus-Edition of HB's until Jim Harrison (and later Gene and Peg Fairbanks) assumed the position of editor.