No, the negative chamber is the same size, and the only 2 parts that have been changed are the foot nut and the seal head.
Annoyingly there’s no pictures of the seal head installed, but see that lip on the seal head? I think that’s where the end of the upper leg sits, with a small portion of the red seal head sitting lower/outside the upper leg. Whereas the current seal head fits 100% inside the upper legs.
Edit: service manual shows it all goes inside, but regardless, the negative spring is still the same size
Which means, the foot nut raises the air piston by 10mm, and the seal head raises the seal position by 10mm. Result: smaller positive chamber by half an air token, and same size negative chamber.
The reason the top out bumper looks smaller is because you’re not seeing it all as its hidden by the seal head.
Rockshox tops up 2021 Pike, Lyrik, Yari & Revelation forks w/ all-new Debonair Air Spring