Does the Lack of an Erasmian Promise Vindicate 1 John 5'7

In 1 John 5:7, there is a debated Trinitarian formula which proponents of KJV-only defend as original. But if Erasmus did not promise to include the formula, known to textual critics as the Comma Johanneum, does that mean the Trinitarian formula is closer to the original text? Bill Brown for the Center of the Study of New Testament Manuscripsts (CSNTM) suggests that the evidence from the manuscripts argues for an original text that does not include the Comma.