It wasn't always his natural weight class. At some point Conor McGregor was a 145 fighter, and he made the weight reasonable well. Then his body grew and couldn't shed the water as easily. So, he accomplished his goals at 145, and moved up to 155.
To say that "155 was his natural weight class" is misleading, because it ignores the fact that at some point, it wasn't. The dude was a scrawny little guy. Then he grew and he had to move up.
I can't dock him points for that. Floyd Mayweather was a little guy (more little), then he grew, and he had to move up. That is how it is done.
TJ is taking months off his life to go down to 125. That is ridiculous, because normally, we put on more weight as we get older, so moving up a weight class is a "natural" progression. In my opinion.