Beats me. I only worked with the easterns. The only time I can recall having egg binding was during one of my earliest breedings. And I blame that on my trying to treat them like typical colubrids. I now believe that the basking spot in the late winter months is critical.
Besides, if you have ever seen indigo eggs, you would be amazed that the females can pass them at all. They are R-O-U-G-H besides being B-I-G! They look like they have been sprinkled liberally with salt. They HAVE to hurt coming out!

I can easily see how a female might give up early if she has delayed laying them too long and they have swelled up.
Speaking of which, when you set up an egg laying box, make sure it is BIG, and make sure the peat moss (or whatever medium you choose) is packed TIGHTLY in there. The female needs to be able to actively BURROW into the medium to make her nesting area. Otherwise she will delay laying the eggs while she tries to find a more suitable nesting site.