I think the idea that most parts aren't already bespoke is a misconception. Everything structural on a rocket or space craft is bespoke. Only built for that craft. Maybe only built a handful of times. So that part is nothing new.

Validation for these designs would be no different than anything else. Finite Element Analisys (FEA) would be used first to evaluate the structure and any changes required to meet the specification would be made before prototyping.

However, what's neat about these procedurally generated parts is that it basically is FEA in reverse. Instead of doing design iteration from idea to part - you just tell it the specification and it designs a part that meets that out of the gate.

The only real downside is that you're much more limited on manufacturability. Either it can't be made using traditional methods and requires 3D printing. Or maybe it can be made on a CNC milling machine but it requires a 7+ axis machine center and takes 100x longer to make. Which for some parts might actually be fine, but for others the added cost would never make sense.

Really interesting topic I'd say.