That would be called under-provisioning.

I haven't read anything about how an SSD deals with partitions, so I don't know for sure.

Since the controller intercepts the calls for specific locations, I'm inclined to believe that the controller does not care about the concept of partitions and does not segregate any chips, thus it would spread all writes across all of the chips.

As the other person said, I don't think the SSD knows about partitions or makes any assumptions based on partitioning, it just knows if you've written data to a certain location, and it could be smart enough to know how often you're writing data to that location. So if you keep writing data to a single location, it could decide to logically remap that location in logical memory to different physical memory so that you don't wear it out.

I say "could" because it really depends on the vendor. This is where one brand could be smart and spend the time writing smart software to extend the life of their drive, while another could cheap out and skip straight to selling you a drive that will die sooner.

It's also worth noting that drives have an unreported space of "spare sectors" that it can use if it detects one has gone bad. I don't know if you can see the total remaining spare sectors, but it typically scales with the size of a drive. You can at least see how many bad sectors have been reallocated using S.M.A.R.T.