Opaque transparency

Nearly a year ago I commented on the AAMD's "commitment" to transparency over the acquisition of archaeological material. One year on I have yet to receive the information that I requested from two (AAMD member) museums about four items that have been acquired since 2002. (Note: these are very recent acquisitions.)

Why are AAMD members reluctant to disclose collecting histories? Why do they send out a signal that they have something to hide?