When i saw him at the weigh-in my first tought was that Cody doesn't look dehydrated at all, so i expected that he doesn't cut much weight. Dropping down to flyweight wouldn't be a bad idea since he has already lost twice to the campion at BW and that usually means that he's not getting another TS soon. I think we might even see a better version of Cody since he would still be one of the hardest hitters in the division but he would have to worry less about his chin since guys at FW don't hit as hard as the guys at BW.
About the eye test, Cejudo vs MM beign a perfect example, i think that some people are ignoring the fact that muscle are only a small portion of your weight. You have to consider water, bone density and other stuff, so a fighter that looks bigger like Cejudo can actually weigh less than MM because he has less bone density for example.