V$SQL_SHARED_CURSOR: when all mismatches = 'N'

Under what circumstances will a cursor be listed in V$SQL_SHARED_CURSOR but have all "N" for mismatches? I looked around in askTom and google, but trying to find the right keywords is tricky. The documentation states:
V$SQL_SHARED_CURSOR explains why a particular child cursor is not shared with existing child cursors. Each column identifies a specific reason why the cursor cannot be shared.

Clearly, I was foolish to take that literally. =) I found a couple metalink notes that reference some older bugs, but they are all fixed in our version.

Oracle 10.2.0.2
cursor_sharing = EXACT

TIA charles schultz
oracle dba
aits - adsd
university of illinois

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