“@see” tag is used somehow randomly
No wonder as any documentation in the end depends on the programmer’s decision of what is worthy of being documented and how.
Documentation in general should not be a verbal description of the code unless the code is extremely non trivial, but add a human friendly summery of what the code does and why. Therefor it is trivial that functions used in the code are not worthy to be referenced in @see as they are already in the code. You should use it when there is some dependence on how a different function works, either because you get input from it in one form or another, or it is going to process your output (very relaxed definitions of input and output here).
So it is down to a judgment call. Will you be able to understand why function A does without knowing anything about function B? If so, the @see is not needed, but if for example A sets a global variable to be used by B, probably both should contain a reference to each other (obviously good code should just not have such things 😉 ).