I believe JEP 401 has not yet been updated to the new model, there is no .val anymore, instead there are nullable value types and non nullable primitive types,

I believe JEP 401 has not yet been updated to the new model, there is no .val anymore, instead there are nullable value types and non nullable primitive types, only the latter has a .ref box because the former is a reference. Optional will be retrofitted to a value class not a primitive class, you get flattening but only on stack (parameter type or return type) not on heap (field). I don't really understand the end of the part3 (the VM model), so i may be wrong.