The only reason I could think of, is that he's very different on the Switch 2 version, but you can play the Switch 1 version on the NS2, so that isn't a real good reason.

Is it just because making him required would cause players to have to go through the CH4 Light World segment? If so, yeah that'll be a section with low gameplay, but you can't call it "All Bosses" and not fight all the bosses.

The name doesn't define the category, the rules do. So you really can call it "All Bosses" and not fight all the bosses.

The origin of the category was to include each chapter's secret boss in the run (when it was just ch1+2) so that concept is now extended to the new chapters. It wasn't made to be some sort of full completion category, and I'm sure such a full completion category would include more than just Mike if it were created.

Also I have a question to add here, in all bosses, do you also have to battle the secret bosses or just the regular bosses and minibosses? (Also in an all bosses run do you also keep the timer on for getting to the next boss or just every time you encounter a boss?)

you can read the rules for each of the all bosses categories on the leaderboard to see which bosses are required

“All bosses” is a category where you fight all the bosses you would normally fight in the speedrun, along with the “secret bosses” of each chapter (Jevil, Spamton Neo, Eram, Knight, Gerson)

Mike is more like a minigame joke fight sort of thing, and it doesn’t involve getting a shadow crystal, meanwhile all the other bosses mentioned above do hand out shadow crystals. It’s the same kind of argument against skipping Berdly and the DJ’s in chapter 2 all bosses.

@Nate09 thank you, but what is Eram?

Eram is one of the two optional bosses in chapter 3. He is a required boss in all bosses for that reason. (You skip him in all shadow crystals if you can beat the knight without the mantle)

Eram (and Nightmare) are alternative names for the ShadowMantle boss

Oh ok.