ALERT: ORA-600 on Standby after switchover

I have been told that SCNs and ITLs are some sacred parts of the ACID test for transactions, but article "ALERT Description and fix for Bug 8895202: ORA-1555 / ORA-600 [ktbdchk1: bad dscn] ORA-600 [2663] in Physical Standby after switchover" found via document ID 1608167.1 on My Oracle Support gives us reasons that both SCNs and ITLs can be violated!