If you SELECT FOR UPDATE a tuple in 9.2, bit 0x0040 gets set in infomask, and nothing else. If you pg_upgrade and later try to freeze such a tuple, it will fail with the error reported.
The correct test to use is HEAP_XMAX_IS_LOCKED_ONLY, which also tests for the above condition.
I will verify this theory and push a patch shortly, if it proves correct.
Oh good news :). I have my old 9.2 around if you need me to do more testing on it.