Yes, SBF and Earnest, and most of those 558 differences are quite minor. There are not many places where in the rev. NWT where the "committee," based on more recent editions of the Greek text, namely NA and UBS, made a change from the old NWT editions. However, one such is at Eph. 1:15.
"Since I have heard of the faith you have in the Lord Jesus and toward all the holy ones," older NWT editions done by Fred Franz.
"Since I have heard of the faith you have in the Lord Jesus and the love that you demonstrate toward all the holy ones," rev. NWT.
The change in bold print is based on the Greek text in NA/UBS. This in turn is based not on any newly discovered manuscripts. In fact, the only manuscript find since the time of WH that bears on this passage is P46 which reinforces the text WH provide, what Fred Franz went with when he produced those earlier NWT editions, and not what UBS/NA read. Rather what has happened is that textual critics (scholars who try to establish what was originally written) have largely changed their thinking here and have come to believe that the words "the love" accidentally dropped out as the text was transmitted down through time. It is not what the earliest sources read. The words in the NWT "that you demonstrate" are not in the Greek but were added for clarity. Overall, what those who are responsible for the rev. NWT often did was look at other modern English translations, often conservative Protestant ones, and imitate them. The NIV, HCSB, ESV, have "your love" here. So do the NRSV and the 2017 NT translation by David Bentley Hart. The NEB/REB has "the love you bear." All these renderings are because the scholars translating them relied on the NA/UBS Greek text, not because of new manuscripts being found.
Two further things. First, WH were well aware of the textual
problem here. They discuss it in vol. 2, pages 124-5. Second, what the manuscripts read is only one consideration of textual criticism. It's called the external evidence. The other area is called the internal evidence, and this includes things like scribal habits, textual transmission and its history, the influence of the church on the text, and so on. WH were aware of both components of textual criticism, but the field has been giving more emphasis to the internal evidence since the time of WH. Hence the change of readings in passages like this. It seems very unlikely that those responsible for the rev. NWT are even aware of details like this. They are just adopting, in certain passages that do not affect their key doctrines, what they see in other modern translations.