A comparison of The Apology of Aristides in Syriac, Greek and Armenian helps clarify how the interpolation "God came down from heaven" in the Syriac came about.
Syriac : The Christians, then, trace the beginning of their religion from Jesus the Messiah; and he is named the Son of God Most High. And it is said that God came down from heaven, and from a Hebrew virgin assumed and clothed himself with flesh; and the Son of God lived in a daughter of man.
Greek : Now the Christians trace their origin from the Lord Jesus Christ. And He is acknowledged by the Holy Spirit to be the son of the most high God, who came down from heaven for the salvation of men. And being born of a pure virgin, unbegotten and immaculate, He assumed flesh and revealed himself among men that He might recall them to Himself from their wandering after many gods.
When you have different text traditions of a passage it is not too difficult to identify where there have been changes. If the texts on which the Greek and Armenian versions are based originally had "God came down from heaven" there is no reason they would have changed that as it supported their trinitarian theology.Armenian : But the Christians are race-reckoned from the Lord Jesus Christ. He is Son of God on high, Who was manifested by the Holy Spirit : from heaven having come down ; and from a Hebrew virgin having been born : having taken his flesh from the virgin, and having been manifested by the nature of this humanity [as] the Son of God.