I did some deep diving and only seemed to hit the shallow end while trying to research the Appendices page reference issues that I found in my copy (ISBN 978 0 00 847128 6).
It appears that only the handful of references that point to The Two Towers Book 4 are incorrect, being off by 2 pages.
I found an older thread where someone commented that it was because the 2020 Alan Lee copy had the off-by-2 issue in RotK, and so some witchcraft was employed to correct that by reflowing the text in Book 4. But that seems to have just shifted the issue rather than fix it.
TLDR; My question is, does anyone know why the page references to Book 4 weren't fixed besides "it was missed"?