When offsetting or thickening surfaces by a value greater than the minimum radius of the surface, the feature just fails. It should display a warning and absorb the intersecting surface creating a sharp edge where the radius drops below zero. The automatic offset is a poor solution. For example, the simple revolve of a spline shown below and attached (Creo 2) fails if the thickness is increased so the radius drops below zero.
A thicken or offset feature that constantly fails when the parent surface is modified is extremely frustrating and significantly diminishes the value of many of the surfacing enhancements and features such as freestyle.
Catia has been able to do this for years and even Autodesk Inventor can do it.
It might be a good idea to have equal wall thicknesses for many manufacturing processes, but surely that is up to the user? - They might add a round at the sharp edge to give a reasonably constant wall thickness, or perhaps add a boss feature or cutout where the problem is. With 3D printing capabilities meaning the thickness is less critical, this becomes even more of a software shortcoming.