I'm curious who the target demographic is for this, people who think they need bare metal performance in a language that gives them access to bare pointers, know that most humans aren't capable of following Uncle Ben's adage[1], and then voluntarily give it up while insisting they need it?

I think almost any JITed memory safe language will be faster than using handles for all object access. At least Java, .NET, JS, etc under the hood can avoid "double dispatch" of memory access. And you can use things like arenas to ensure same objects are allocated adjacently, etc.

[1] With great power comes great responsibility

The solution presented solves "memory corruption" from the point of not having undefined behavior, but it doesn't really protect against "I accidentally created an index that has nothing to do with memory I manage, but is still 'in bounds' to the code that handles lookup".