# Why is the following reaction not considered a redox reaction?

The following question appeared in the Cambridge International AS and A level Chemistry Coursebook:

Choose from redox, substitution, elimination, addition and hydrolysis to give the type of reaction for the following: $$\ce{C2H6(g) + 2Cl2(g) -> C2H4Cl2(l) + 2HCl(g)}$$

The answer given by the answer key was substitution since $\ce{Cl2}$ replaces $\ce{H2}$.

However, why is redox not a suitable word to describe the reaction? After all, the oxidation number of $\ce{C}$ in the reactants is $-3$, while it is oxidised to become $-1$ in the products. Furthermore, the oxidation number of $\ce{Cl}$ in the reactants is $0$ while it is reduced to $-1$ in the products.

Hence, by that logic, isn't the reaction also a redox reaction since $\ce{Cl}$ is reduced and $\ce{C}$ is oxidised?

Thanks in advance for any help.