What might cause OCILobIsTemporary to give an incorrect result?

I'm seeing a case where I've had to keep track of which LOB locators are temporary because I can't trust OCILobIsTemporary to give an accurate result.   I'm seeing cases where it starts returning 0 instead of 1 for all my temporary LOBs.   It seems to happen when the LOBs are used as bind values to UPDATE statements, but not for INSERTs.  I'm seeing this with Oracle 10.2.0.4 and 11.1.0.6 

I'm posting in the Precompilers community because I haven't been able to narrow down a test case yet and I can't find anything in Metalink on it.

The SecureFile and Large Objects guide says "

A temporary instance becomes a persistent instance when you insert the instance into