Actually, your odds are probably even better with normal pythons coming from captive breeders...many people sell low-percentage hets as normals. It's not worth trying to market a 25% or lower chance het, so they simply go out as normals.
Some people don't even bother with 50% chance. I even know of a handful who don't bother to market anything other than a 100% het, and sell everything else as normals.
Granted, you have a lot of 'normal sibling to pastel or spider', but people who have been breeding ball pythons for many generations are more likely to hold back offspring with possible recessives than they are to hold back absolute normals.

Without a doubt there are ball pythons not carrying any recessives for color or pattern mutations.
Keep in mind that it's also possible for them to be carrying recessives for undesireable or even lethal defects.