SQL Server 2016 deprecation of DML keyword ROWGUIDCOL
I think you are misreading the deprecation notice. Specifically, you seem to be confusing DML (Data Modification Language) with DDL (Data Definition Language). What is being deprecated is the ability to use ROWGUIDCOL in INSERT / UPDATE / DELETE / MERGE statements:

-- DDL statement
CREATE TABLE #Test
(
  ID UNIQUEIDENTIFIER NOT NULL PRIMARY KEY DEFAULT (NEWID()) ROWGUIDCOL,
  SomeColumn INT NULL
);

INSERT INTO #Test ([SomeColumn]) VALUES (1), (100);

SELECT * FROM #Test;

DECLARE @RowID UNIQUEIDENTIFIER;
SELECT TOP 1 @RowID = tbl.[ID]
FROM   #Test tbl;

SELECT @RowID AS [RowToUpdate];

-- DML statement
UPDATE tmp
SET    tmp.[SomeColumn] += 2
FROM   #Test tmp
WHERE  ROWGUIDCOL = @RowID;

SELECT * FROM #Test;


If you run the above, only one row will be updated. This example shows that ROWGUIDCOL when used in a DML statement (not in a DDL statement) is dynamically replaced with the actual column marked as ROWGUIDCOL. And this is, in fact, why you are able (or required?) to mark a column as ROWGUIDCOL in a DDL statement: so that you (and other processes) can find it later :-).