Chopper has his 7 Points that have been established since the Drum Arc. These are Walk Point, Heavy Point, Brain Point, Arm Point, Horn Point, Jumping Point, and Guard Point.
Now, in Enies Lobby, he turned into a "monster," in Chapter 407: Monster.
Now, he has a new point called Kung-Fu Point.
What this chapter is trying to establish is that "Monster" was never a Point. It just began being called one, but Chopper himself has never called it a Point. He has never announced it as a Point. It just became the "name" for it. Oda never seems to acknowledge it either. Chapter 407 is not called Monster Point, it is called Monster. Chopper is separating the Monster Form from his Points in this chapter. Chopper is, in fact, saying afterwards that he can also be a "monster." Thus, Monster Form is not a Point.
Now, Kung-Fu is not replacing any of his points. It is his eighth point, true. But, let's do the math. Chopper says at the top of Page 12 of Chapter 636 that he can change into his OTHER 6 whenever. On the page before, he says that there is a separate form he can change into that requires his rumble ball. So, he says his OTHER 6, so Horn is 1, since he is in his Horn Point, then his other 6 that he can use whenever he wishes. Then the is the 1 that he needs to use the Rumble Ball. 1 +6 + 1 = 8. This make 8 in total. So, that is not a plot hole.
Involving the identity of the Point that requires the Rumble Ball. As mentioned by other posters, I am going to figure that this may be Guard Point. Either that, or it may be Kung-Fu Point, being the newest, and he possibly ingested a rumble ball off-screen. This would mean that we may be receiving an explanation that a rumble ball increases the uses of the techniques to fix that in the plot.
My personal theory is that guard point is bigger because it has been improved, just as it seems that his other abilities have been improved, like Chopper said. But, considering he ingested a Rumble Ball when he was using Guard Point earlier, then I can only figure, at this point in time, that Guard Point is the 1 Point that still requires a Rumble Ball.
Alright then, now that I got that out of the way, let me just say that I felt that this chapter was definitely better than the last one. Nami, Usopp, Chopper, and Franky are all so amazing and badass. To be honest, the Weakling Trio don't seem very weak anymore. In fact, so far, I think Usopp and Nami are fantastic. I REALLY want to see more of them. Chopper is much improved. I'm so proud of that little cute goddam reindeer!!! Franky is freaking amazing. I can't believe he made a giant robot and gave Vegapunk kudos. Epic.
I understand where others are coming from when they say that this arc is not really challenging, but if you notice, neither was the first arc of the show, the Captain Morgan arc. When Oda introduced Shirahoshi, and had Luffy call her weak, similar to Coby, I think it means that Oda is trying to mirror this arc as the New Word version of the Alvida/Captain Morgan Arc. Since Oda had Fishman Island as the first major arc after the timeskip, I feel Oda didn't want to make a quick little arc. So, he made an arc with back stories and new characters just like all of his past longer arcs. But, to reflect the first arc of the show, Oda wants the villian to not be on the same level as Luffy. The same goes for the rest of the crew. Now, many of the enemies are sort of fodder in power level compared to the Straw Hat crew. We are being reintroduced to everyone's powers, and Oda is reestablishing the power status of the crew, just as he did at the beginning of the show with Luffy and Zoro.
So, my feeling is this. Hody is an average villain. But, he was meant to be an average villain. Not a bad villain, but not a great villain either. But, there may be more to the arc, maybe a different villain may come out of nowhere. I can't really say. But, what I can say is that I won't be mad if this arc is primarily how we see it as it is now. Just this fight, and then the arc is over. I will agree that as a villain, Hody could have been better developed though. Maybe Oda was rushing because he was itching to get to where he is right now with the story because he was excited to show off the new Straw Hat powers. I can't say. But, what I will say is that I wouldn't be surprised if there was a certain way that Oda wanted Hody to come off, and that he didn't want Hody to be this crazy, well-developed villain, just like Alvida/Captain Morgan. Oda wanted Hody to be an average villain. This is just my theory.