My family is from Sicily, and I remember taking this train every year when I was a kid. After several years, I took it again last summer and was bufflled at how inefficient the whole ordeal was... Basically you have to wait for the train wagons to be detached and reassembled on the other side, you easily waste a couple hours.
Now, I don't really mind this, it's a bit of a tradition if you want, but I asked a relative of mine who used to work for the Italian national train company, and he told me that this train works like this cause in the past all the Sicilian migrants would travel with a lot of luggage, and it would be very impractical for them to transfer all of that twice. Nowadays this is not really the case anymore.