VueJS: changing the binding parameter of a custom directive?

Question

Vue.js

I decided to write a couple of directives, looked off. documentation and source codes for vue awesome directives.
It seems that I figured it out, everything is clear except for the moment with the parameters of the hooks.
Off documentation says:

All arguments other than el should be understood as read-only and should never be changed. If you need to pass information between hooks, we recommend using dataset.

Okay, everything is clear. Now I look at the source code of the v-dragged directive and see that on line 16 there is an entry in the binding parameter.
Tell me if I understand correctly that the author has departed from the recommendation in the off. documentation and wrote not quite correct code (although working)?
Or did I not understand something?

Answer 1

I see that in line 16 there is an entry in the binding parameter

Where did you see this, I don't know. Calling a function parameter is not "writing to a parameter" at all.