What if he clock-ups right before all of those?
He breaks his freaking hand on Shining Agito's armor. Speedblitzing is fantastic, but just because you CAN hit something, doesn't mean you SHOULD. Particularly at an especially high speed.
But he doesn't have to physically hit Shining Agito, he can shoot him to death with G4's rocket launchers while dodging in light speed.
He doesn't have G4's rocket launchers. You don't see him using IxA's stuff. Main Rider equipment only. (Does Fury Form prove otherwise?)
...And if he did, so what? They're not on the same level.
The Script said:[EXTERIOR - DAYTIME]
Decade
UNGH!
[Decade loses.]
he used it in conjunction with Kaixa's SideBasher to kill Kamen Rider J in giant form. We can also assume he can fly.