The reasons given in the Appendix have a little to recommend them, but are somewhat disingenuous even so. Of more importance is the claim to respect evidence from the MSS. which is their reason for not including certain verses, i.e the Pericope de Adultera in the Gospel of John.
But they have NO N.T MSS. that contain the divine name in the places they insert it, therefore their claim as to sticking to the witness of the earliest MSS is a falsehood.