“Hybridisation of central atom does not always change due to back bonding.” This statement is valid for which of the following compounds ?

In $CC{l}_3$ and $CC{l}_2$, the back bond formed from lone pairs of Cl to Carbon atom, which is a pi bond. So Carbon hybridization does not changes.

In ${\left(Si{H}_3\right)}_{2}O$ and $N{\left(Si{H}_3\right)}_3$, the lone pair of O, N forms pi bond with Si vacant orbitals. Due to this hybridization of O, N changes.