Is there a reason why $\text{Arg}(z)$ behaves like a logarithm?
The imaginary part of $\log z$ is $\text{arg}$ z.
$$\log z = \log |z| + i \,\text{arg } z$$
The imaginary part of $\log z$ is $\text{arg}$ z.
$$\log z = \log |z| + i \,\text{arg } z$$