It is not exactly that K and O must be placed before L. It is that both Ks must be placed before O, but O must be placed before "at least one of L". This means that the other L is free to be in slot 1, forcing the L to not be allowed in 9 in this scenario.
That is the reason that we cannot outright determine that L is 9. Had the rule stated that all Ks before O, and O before all Ls, then we would know that L is not 1 and therefore, must be 9.
I hope this helps. Please let me know if you have any other questions.