Don't know what you mean by highlaner, but here is my thing about GC in an exodia deck, This has happened fairly often with exodia users form my experience.
Check this: You have a hand of nothign but exodia parts, two parts plus GC. YOu activate GC, and two of those cards you drew are Exodia parts. now you're in a dilemma. You have only one non exodia part in your hand, but you ahve to discard 2. Plus, with Cards like Null and Void out, if they were to activate that not only would you discard the three cards you just drew but you'd stillhave to discard two more from your hand. So then according to this situation if they activate Null and VOid, you're otu of a hand.
The situation varies slightly each time, but that is the basic principle of it.