I watched the linked original video to understand the motivation, and read the article, and I think this is a misguided solution to a real problem.

These "joint allocations" seem to be "a small pool of heterogenous types." The motivation is that heap allocations are expensive, so we want to coalesce them. The only way this would matter at all is if we are creating lots of these Mesh objects.

The given solutions make one heap allocation per Mesh object, as opposed to three. Create six million Meshes and you get two million allocations.

Instead, one pool should be created for each of the three array types: Vector2, int, and Vector3. Now, create six million Meshes and you can do somewhere between three and a few dozen allocations, depending on your pool's initial size and growth strategy.