To be fair, you don't really see that type of arc until a manga hits its stride, because of the large number of chapters it needs to span. You keep it in monster of the week mode or short character introduction/building arcs until then. But really, he should have saved it until the manga hit that point.
The bolded is certainly one thing you can lay against it.
Though equally, if one
must do it this early, well... there's ways to do it better. Like, as a quick point of reference, I decided to go back and check just where exactly Dragon Ball - template of most modern shonen - was at around the same chapter count, since it too made its big tournament arc -
the tournament arc - its second major story arc.
So in Chapter 33 of Samurai 8, we have wrapped up this whole shebang, including the reveal that the tournament was being used by the forces of evil for some nefarious end that redirects the story to dealing with that instead.
In Chapter 33 of Dragon Ball,
Goku and Krillin have just arrived.
Even if you count it in terms of from when each arc started - chapter 17 for Samurai 8, chapter 24 for Dragon Ball - by 16 chapters in (to match Samurai 8 being at chapter 33), Dragon Ball was still resolving Goku vs Giran, aka round 4
of the quarter finals.