two questions on allocators

[Mehdi Saada <00120260a@gmail.com>]

2.2/3: for an allocator with a subtype indication, the subtype indication shall not specify a null exclusion
why 
type A is access INTEGER;
type B is access not null A; 
type C is access B;
Object_C : C := new B;
is allowed, but not
type A is access INTEGER;
type B is access A; 
type C is access B;
Object_C : C := new not null B; ?? What's the difference ?
_______________________________

If the designated type of the allocator is class-wide, the accessibility level of the type determined by the subtype_indication or qualified_expression shall not be statically deeper than that of the type of the allocator.

-> what means the last "type of the allocator" ? Is it the same than "designed type of the allocator" ?
Does it refer to this situation ? ->
type T is access some_tagged_type'Class;
POINTER : T;
declare
   type CHILD is new some_tagged_type with ...
begin
   POINTER := new CHILD; --illegal
end;

Technical details of this section aren't gonna matter for me any time soon, so that will be all.