Ah, you're right, thanks for correcting me! This also doesn't apply to heap-allocated variables, though I think p2795r2 should cover all these cases.
I wonder if (for stack variables) this is due to an implementation detail in the compiler. After all, non-trivial classes have 'actual' constructors that run and that is supposed to initialize their respective class instances...
I believe this only helps for trivial automatic variables; not non-trivial automatic variables (structs/classes) that contain uninitialized trivial members.