Going back to the singular announcements this may be something they've been playing around with for a while possibly for games that are of a certain tier or possibly a strategic element behind it with them in future doing NDs then a month later dropping an announcement. An example could be they do an E3ND showing their main line up in the year then in July they drop an announcement of Golden Sun (example) releasing in September that wasn't in the E3ND, although a fan favourite series it's obviously not on the same mainstream power as the evergreens so such an announcement is more suited for such titles.