True. If Cath wanted to be sure to avoid blasphemy then at least they would be careful to call her the mother of God the Son. RCs even refrain from calling Mary the Theotokos as "God-bearer," which is less likely to be misunderstood than "Mother of God," since that naturally denotes ontological oneness.
But instead RCs insist on the most easily misleading term, as they are either ignorant or would rather exalt Mary as a demigoddess than be careful to avoid fostering a blasphemous idea about Mary.