Delphi interfaces and class variable types

I have read that interfaces are a good thing to decopule the code and Nick Hodges has written a good chapter on it. Reading that I have produced this code:

//interfaces
type
 ILocalization = interface
  ['{1D144BCE-7D79-4672-8FB5-235422F712EE}']
  function localize(const aWordId: string): string;
 end;

type
 IActions = interface
  ['{31E8B24F-0B17-41BC-A9E4-F93A8E7F6ECF}']
  procedure addWord(const aIndex, aWord: string);
  procedure removeWord(const aIndex: string);
 end;

//implementation
type
 TLocalization = class sealed (TInterfacedObject, ILocalization, IActions)
  private
   FTranslationList: TDictionary<string, string>;
  public
   constructor Create;
   destructor Destroy; override;
   //interface implementations
   function localize(const aWordId: string): string;
   procedure addWord(const aIndex, aWord: string);
   procedure removeWord(const aIndex: string);
 end;

I am planning to use this class to localize (translate) my delphi android apps.

When I am going to make an instance of the class I do the following.

var
 Italiano: TLocalization;
begin
 Italiano := TLocalization.Create;
end;

Since TLocalization should have inherited AddRef and Release I won't try finally this, but does this happen even if Italiano is a class type and not an interface type?

What I mean is this:

• Italiano: TLocalization -> here I can use all the methods
• Italiano: ILocalization -> here I can use only the localize function

Given the fact that (as I've already said) TLocalization inherits the AddRef and Release I don't have to free if I have understood correctly. It should be the same with ILocalization but does it have other benefits? I don't understand what are the differences of the 2 cases above