It means that the Cardinal knows what this is all about. Non-catholics should not give any malice to this since they do not know anything about Hebrew.
So, the question is why is ADONAI used instead of merely pronouncing it “YHWH”?
Because this is the Hebrew text, ”Adonai” אדֹנִי
and this is the Hebrew text of “YHWH” יְהוָה.
This is what is written in the Masoretic text.
Let us look at Exodus 6:3, (YHWH) tetragrammaton is read as “Adonai”.
So, why did you read it as Adonai?
According to Jewish Tradition, there is a restriction in reading YHWH.
That is why Adonai (אדֹנִי) was used instead of YHWH.
Adonai is used by the Jews every time they want to read the name of God.
We will see the Plural Ending in the Hebrew word, ADONAI.
The plural ending is “Plural of Majesty” from the Word Elohim.
There is a dominant tradition among Jews about tetragrammaton and this should be read as Adonai.
So, there is no problem at all since what they are doing is right.