When the person (who uploads the averages) uploads new data, then people are normally replying to that new data. But, this time, people basically ignore that which is unusual. So, I think it is most likely that ToC is fake. (1)
I forgot about Beelzebub's length, but Kuroko's length is same as regular chapter (19 pages). But, I don't think the editors tell the author to do 50 pages within one week; I think it is more like the editor tell them beforehand, so the author can do the special chapter whenever they have free time after the regular serialization. Plus, based on Komi has to do the one shot and full color chapter by Issue 6/7 as well. Even though there is one extra week to work on, it is still lots of work for two weeks. So, I think Komi was working during his free time. So, I don't think Saeki was forced to do the two chapters within one week. (2)