I am pretty sure the manga has never stated something like that and let's say if what you stated is correct, why would Guy make a fighting style to avoid genjutsu when he could simply open 1 gate and be immune to genjutsu.
If you release a gate, the sudden release of chakra should be able to release genjutsu. Plus, he doesn't spam gates until the situation calls for it.The ninja needs to stop the flow of chakra in their body, and then apply an even stronger power to disrupt the flow of the caster's chakra; this is called Genjutsu Dissipation (幻術解, Genjutsu Kai). This can also be done by an unaffected ninja by applying a sudden surge of chakra into the affected person. In addition, tailed beasts can break their jinchūriki out of genjutsu in a similar fashion if they have a good enough cooperation, as seen in Killer B's case.