Someone already proposed two answers to this question and they are last minute changes on where items/ninjas will be and not allowing people to prep. If those are the reasons why Oasis won't disclose, of course they won't say so.

Did you really expect him to re-appear in events back to back? You might be over thinking it.

It's on who has access to these ninjas is the issue. It's obvious that whales will get to use them first while f2ps, on average, take longer. Of course, not all ninjas will be good but an increased rate of releases doesn't help some players being able to use these ninjas.

People rely on meta because they want to win (not a surprising reason) and some don't have the luxury to switch teams that can replicate their win counts.

Of course whales got stuff before the majority of the community but the time between when the two players have getting stuff have gotten larger due to increased releases as the majority won't keep up.

Up until October/November 2017, it was easy to track when stuff were going to be release on our server based on what was released on China (2 year gap) then on Germany (1-2 month gap). Due to this, planning out coupons/ingots/seal scrolls was very easy to do. After that date, it was hard to predict from China because we got shisui which was earlier than expected so people went to check for Germany releases. A couple of months later, Germany releases were becoming random compared to our server with one server getting one thing earlier than the other. A little after that, we started to see ninjas/clothing being release a faster rate than months before. Personally for me is it is not about them getting stuff earlier every time, its about how accessible can it be for the whole community. I can say for the rest of people with this worry as they might have different reasons like jealously, want to be a collector, worry about game balance, etc.

There is one thing to point out, this game is after all based on an anime. We know the Naruto/Naruto Shipudden series has ended and integrating the Boruto series does not make sense as it should be a stand-alone game. based on this, story content will dry up quick if we catch up to China (which only has a little more canon characters left unless they want to continue adding non-canon characters). Some people would quit since they don't see anything new from the story line unless they stay for game content.