Why cannot claim OD KFK?

If you're saying it will turn into OD, meaning claiming TP also will not succeed isn't it?

According to what I know, can proceed with OD first, once get confirmation is Third Party fault, then can convert into OD-KFK.

allowing OD to OD-KFK is at the mercy of your insurance's claim staff:
I don't agree on this part. As long as all the necessary documents are submitted later (provided it is confirm you're not at fault), the status will be changed and NCD will be revert back. I have been working in insurance company, there is no such thing as "at their mercy" throughout my experience.