Under "Modify the description of GetCompressedTexImage:", it says:
called, GetCompressedTexImage and GetnCompressedTexImageARB write
MIN(n,bufSize) ubytes of compressed image data ...
This is inconsistent with every other entrypoint, which doesn't have that language. It also contradicts the "Errors" section, which includes GetnCompressedTexImageARB in the list saying "INVALID_OPERATION is generated if the buffer size required to fill all the requested data is less than <bufSize>" (and according to the "GL Errors" section of the OpenGL spec, INVALID_OPERATION means the "offending command" is ignored) as well as the resolution to Issue #5.
Rev 15 of the extension (which may have been posted shortly before you
filed this though I'm not sure) corrected the error condition to be
"... *greater* than <bufSize>" rather than "less", so the inconsistency
has been resolved.