Comment by jayd16

More than the trying to find another object kind of math, I was mostly thinking about address aliasing ie cleared handles pointing to re-used space and now live but different objects. You could just say "don't screw up your handle/alloc code" but it's just something you don't have to worry about when you don't roll your own.

The live C# but dead Unity object trick is mostly only useful for dangling handles and IDs and such. It's more that memory won't be ripped out from under you for none Unity data and the usual GC rules apply.

And again the difference between using the GC and rolling your own implementation is pretty big. In your hash map example you still have to solve the issue of how long you keep entries in that map. The GC answers that question.