Insurance Claim - Alloys wheel not being repaired

Recently I got into an accident.

I notified the insurance, telling them the bumper has been damaged alongside an alloy.

I went to collect the car today from the repairer and they told me that the insurance company rejected the alloy wheel repair. The note rejected note stated that the alloy had some previous curb damage. Strangely, they replaced the tyre but not the alloy itself.

The alloy had very minor curb damage beforehand however it has been completely scratched because of the accident. The car is over 5 years old.

I called up my insurance company and they told me that the IMS Engineer rejected it and they have asked them to reassess it.

My question is, is this normal? What can I do?