The first one is because $$\text{csch}^{-1}(-x)=-\text{csch}^{-1}(x)$$ On the other side, in the real domain, $\text{sech}^{-1}(x)$ is undefined.
The first one is because $$\text{csch}^{-1}(-x)=-\text{csch}^{-1}(x)$$ On the other side, in the real domain, $\text{sech}^{-1}(x)$ is undefined.