It's explained pretty well in the answer to Use of the term "consecutive" to describe a single item, on Stack Exchange itself:
First note the context in which these examples are presented - namely in the context of programming.
It is true that colloquially we would not say that there is one consecutive instance of the digit 1. However, in the more formal setting of programming it is desirable to handle exceptions without dealing with special cases. This is because case handling is generally considered to be inelegant in programming.
It's about something bit different, but fits in this case as well, where it's applied to a single day.
If you want this changed, it's possible to start a feature request asking to hide the whole element in case there are less than two consecutive days, as Cave Johnson mentions in this comment as well.