And there is a difference between the word כי (when it is used as “rather”) and the words כי אם (only if):

Any place where it comes to impose a condition on the previous negation – that it will not be in any manner except in this manner – the words כי אם will come. [The word אם is used with the condition, and it usually means לא יהיה הדבר רק אם יהיה בו תנאי זה (the matter will only be if this condition will be), like יאכל מן הקדשים כי אם רחץ בשרו במים (יאכל) לא (and shall not eat of the holy things, unless he bathe his flesh in water)⁵³⁶. And also in a place where the condition is not mentioned explicitly: לא ירשך זה כי אם אשר יצא ממעיך (This man shall not be your heir; but he that shall come forth out of your own bowels shall be your heir)⁵³⁷ – it means to say that inheritance should not be elucidated in any manner other than to his own children.]

footnotes: ⁵³⁶ Leviticus 22:6. ⁵³⁷ Genesis 15:4.

But the word כי is never connected with the previous.