Could be - it looks like a case that could go either way. New Testament scholar James Dunn categorises it as an ambiguous use of kyrios that could apply to either God or Jesus. The NWT study Bible makes a reasonable case for their inclusion of Jehovah in the verse based on the context:
In the preceding two verses, Kyʹri·os occurs twice. In both cases, it refers to God and can be viewed as a substitute for the divine name. (See comments on Acts 13:10, 11) The expression “the teaching of Jehovah” is synonymous with “the word of God,” used at Acts 13:5. That verse says that when Paul and his companions arrived in Cyprus, they “began proclaiming the word of God in the synagogues of the Jews.” As a result, the proconsul Sergius Paulus was “eager to hear the word of God.” (Acts 13:7) So it is natural to conclude that after witnessing what Paul said and did, Sergius Paulus was astounded at what he had learned about Jehovah God and the teaching originating from Him. Some translations of the Christian Greek Scriptures into Hebrew use the divine name here. So in view of the context and the background of the expression and the ambiguity of the term Kyʹri·os, the divine name is used in the main text.