pretty much this.
People with large chakra pools and good chakra control(ie hashi) are more capable of escapeing strong genjutsus, but some genjutsus, appear to be unbreakable unless there is a other person who will dispel the genjutsu. As a perfect jin always has a partner able to disrupt his/her chakra, Perfect jins are possibly immune to all genjutsu.
KA, and MAYBE tsyukiyomi, are unbreakable(or not easily broken) by a perfect jin. KA is probably the only one a perfect jin cannot break, as it is subtle, and is not based in illusion like other genjutsus.
Also presumeing that the target perfect jin is similar to kabuto(trying to avoid who he/she is) izanami would not be able to be broken by the bijuu(but still easily escapeable)
edit
I think a perfect jin can dispel tsuykyomi, but would probably be caught in its effects some....so an itachi grade tsyukyomi, would inflict harm on the jins mind, but would still be breakable.(if this was untrue, then itachi couldve just collected all the jins with ease, as only a few were perfect jins)