I agree those 3 can be a coincidence, but it also has the possibility of being a pattern. We will find that out early next year
BotW has much more weight as a launch title than as a March game. It would have come out any other time along with the system.
I was actually just referencing Nintendo developed games. There surely are plenty of successful sales of various games of diverse genres release in march.
MP4 could do well at any time, but it has to have the necessary exposure. It's not an easy sell. To give it a boost I hope they drop the 4 and give it a subtitle.
I agree that more games should release once they are done and be better products. However, we also need to consider the financial implications. Pokémon for instance, is a much tougher game to delay because of all the other sources of income that revolve around the launch of a new game (merchandising, TCG, anime, movies...). There's also sales. If it sold well, they have less incentive to change. That being said, in 2021 we only get DLC for S&S. Maybe in 2021 we get Let's Go Johto and then in 2022 we get the remakes for Gen 4. They will have had a lot of time to improve the performance of the more open areas and have all Pokémon in the game. It's a possibility.