Solved - ([GAMEPLAY] "Unique passives" 10%/20% cooldown reduction actually stack)
As in the title - unique passives are not supposed to stack but they seem to do in this case (maybe for the 20% of Nashor's Tooth it's intended, anyways happens also with two 10% items).
Edit: I didn't see in the rules when it says that non-named passives can stack for different items - not a bug!