If the Corbin works just right for you, that's good. I had a used BMW K75 with a Corbin. It was too wide for me. My seat pro explained the situation.
In Corbin's manufacturing, the seat pan is poured plastic. After that, the padding is poured onto the pan. They have a tendency to melt together in the manufacturing process. They are very difficult to modify.
When an experienced pro makes you a custom saddle, the saddle will be fitted to you. It will be the right width, height and angle. Also, you and he can determine any height variations front to back. In short, the fit won't be close, it will be precise.
I need to have the saddle width fit me. Otherwise, my hip joint gets grumpy. I found this out by doing delivery rides of the KZ 900/1000s to customers of the shop I worked at.... some years ago. The big Zs are wide and so are their seats.
The process is like going to an Italian tailor who measures you for a fitted suit.