I think I managed to pierce the mystery linking the TOC and WSJ poll result.
What I did was compiled the TOC result for the 25 firsts chapters of every new WSJ series since 2011, from "Dois Sol" to "Sporting Salt". Then I sorted them by number of chapter as a way to sort them by successfulness (Series with 25 chapters or more were categorized as "25+").
Here are the data I get formated as a Table:
(I cut some series because some of their key chapter were unranked because they were color page)
At first, I did not see anything abnormal but after some more observation, I saw something strange the that color vomit.
5 new series that lasted between 18 and 20 chapter experienced a significant decline in the TOC at the 7th chapter. But because my color code was was not really accurate, I decided to investigate more deeper by analyzing all the change of rank during the seventh chapter for the all the new series. I calculated the change between the chapter 5 & 6, 6 & 7, and 7 & 8.
Here ar the result:
I do not ask you to understand all the chart, myself I had difficulty in understand it after I created it.
I want to bring your attention to the part that I have circled in red. The red line represents the difference between the chapter 6 and 7, the higher the number, the higher was the decrease was significant between the chapter 6 and 7, meaning that something happen to those series at the 7th chapter. The series included in the red circle are the series between "Shinmai Fukei Kiruko-san" and "Takamagahara" in the table above.
Those series have in common that the lasted between 17 and 24 chapter, meaning they were canceled at their first editors meeting which also mean there is a good chance that their first chapter have been badly received and voted.
I think this is a good evidence that the TOC reflect the WJS poll result and that the lag between the chapter and it's rank is 7 chapters.
I could be wrong, but coincidence it would be a huge coincidence that 13 series on 40, which have all in common that they were quickly canceled also have also all had a drop in the rankings for their 7th chapter.
TL;DR The TOC ranking represents indeed the Weekly Shonen Jump Poll which reader sends every week and the ranking for the new series begins at 7th chapter and not the 8th contrary to what everyone thought.