How is this different from simply changing 𝐴 𝑠 A s ​ or 𝑛 𝑠 n s ​ ?

[GeometricCosmo]

Unlike changing the overall amplitude or tilt, this suppression is scale-localized.
Large scale modes (well constrained by Planck) are untouched, while only the damping tail regime is modified.

This breaks degeneracies with $A_s$ and avoids degrading the excellent low-ℓ fit.