I don't think it is a good habit for the devs to have but if it has been happening for years, it is undeniably a habit.
I know they always show the earliest possible date as the expected release date, which is a mistake which is entirely a bad communication practice and only harms the devs.
If such a date is, like in this case, end of the month, and then they release the game first week of next month, they would have to give the game to subscribers of 2 months instead of 1 month. In the case of this dev, they have missed such windows by a month at times and have given the game to $10 subs of 3 different months.
It doesn't really harm the patrons (other than being disappointed) as much as it harms the devs, I think everyone has communicated that to them numerous times but they keep doing it, somehow. Just don't give a date, if you expect end of month release, don't even give the month.
As for myself, since OCTOBER, I expected the release to be around Jan (or even first week of Jan) right when I heard "mid December". Failure happens only when you have expectation