This simply can't be true.
This must be a propaganda dream of the Derg...
From mouth to mouth story until it was written down in the Kebra Negast it was always kept that Solomon had a son with the Queen of Sheba: Menilek. This is the start of the Solomonic lineage of Ethiopia.
There would be absolutely no reason for HIM to drift from that view.
If He would have disavowed, then WHY the title "LION OF JUDAH"?? why the Davidic (Solomonic) STAR on the Emperor's flag, crown, military insignia, University Campus? Why the solomonic star connected with the Trinity sign and not the Trinity sign alone??
WHY all this? For a joke??
When His Majesty once had dinner with Israeli statesmen, they said to HIM: "Oh, your country's narrative of Solomon and Sheba is a pleasant tale" He responded:
"This is no TALE!"