Its interesting that we consider the scheduling for all these games a problem when Steam, PS4, and Xbone get as many games, if not more, and all within certain quarters.
As I mentioned before, Nintendo are probably thinking that having a relatively bare Spring quarter (if you think its bare) for stacked Summer and Fall quarters leading up to the holidays. During the holidays, they already make more than half of their revenue around that time, at least in the Americas.
But things can happen such as delays. Unfortunately, Fire Emblem Three Houses needs more time and couldnt make the Spring release.