Comment by boroboro4

The core insight there is to separate value semantics (no identity) from reference (itself) semantics (nullability). While this particular change can bring very limited amount of improvements it’s still does some - probably smaller to no object header + more guaranteed optimizations for variables on stack.

It’s when they land next part (nullability) it will shine fully - particularly on the intersection of not null and value. Alternatively if they introduce tearable semantics it will also shine - it would be possible to still optimize array of value classes, even if they are nullable (for example by having correspondent nullability mask).

So they are taking right step in a right direction. They are just trying to land this incrementally.