On reading #37, the irregularity regarding Mark 16:8 is resolved in this way: in the 2003 "A Reader's Greek New Testament," the Gk text put together by Goodrick & Kohlenberger presents exactly what the SBLGNT apparatus says that "NIV" presents: the end of v. 8, followed by the Shorter Ending, followed by the Longer Ending.
So given the SBLGNT's definition of "NIV" as the base-text presented by Goodrich and Kohlenberger, its apparatus-note is completely correct. It's Goodrick and Kohlenberger's text-reconstruction that is apparently incorrect, inasmuch as the NIV has, afaik, never presented the Shorter Ending after Mk. 16:8. (The Goodrick-Kohlenberger text is supposed to be "the eclectic text that underpins the New International Version." Just maybe, Goodrick & Kohlenberger made their base-text from a form of the NIV that goes back to 1973; I do not have a 1973 NIV NT to check this theory; it is conceivable that some early form of the NIV presented the Shorter Ending, and that that short-lived form is what Goodrick & Kohlenberger represented as the base-text. If that is the case, though, then the Greek text put together by Goodrick & Kohlenberger might represent a 1973 NIV, not the usual 1984 NIV.) So when comparing the SBLGNT apparatus-notes to the 1984 NIV, it's important to notice that "NIV" does not mean the NIV; "NIV" = Goodrick & Kohlenberger's reconstruction of the NIV's base-text (which is not at all representative of the actual 1984 NIV as far as the ending of Mark is concerned).
But who really cares about the base-text of the 1984 NIV anyway, especially since its own publisher is in the process of replacing it? The important thing to see is that "NIV" in the SBLGNT apparatus shares the same content as the NA27 text (except where they both are listed). That is the only real value of the references to "NIV" throughout the SBLGNT apparatus.
Yours in Christ,
James Snapp, Jr.