That is correct: "God (Gr. Theos, vs. the Heb. HaTzur, 'The Rock'), His works are true, and all His ways are equity. God is trustworthy, and there is no injustice in Him; just and sacred is the LORD" (Deu. 32:4, LXX).
A similar mistranslation occurs in 2 Sa. 22:32, this time replacing Tzur with Ktistes, altering, "Who is a Rock except our God?" to "Who is a Creator like our God?"
Good catch, A-G.