The problem, in my case, turned out to be that I was using the wrong field. I should have used "InventorySiteRef" rather than "InventorySiteLocationRef," which referes to a bin number within a site. Once I made this correction, everything worked.
The problem with "InventorySiteLocationRef" remains, however. It's a legitimate field in QBFC, and the supposedly all-knowing Onscreen Reference from Intuit does not indicate that it may fail. Fail it does, however, for many if not all versions of QB. I finally found, in the QBFC 12 Release Notes, a rather extensive list of fields that appear to be legitimate, but don't actually work. Here's how Intuit describes them. You can search for this text to find the list in the Release Notes:
NOTE: A majority of these changes have NOT been implented in Quick- Books. These are spec changes only to allow for implementation in a future release of QuickBooks.