You may think that if you have had an accident and it’s not your fault, that you can claim for all the injuries and damage you have suffered.
However, there is a legal principle that the injured person is expected to have taken all reasonable steps to protect themselves from injury. If not, then the other side may be able to pay less in compensation. For example, if you have massive injuries to your feet because you were only wearing flip-flops, or even flimsy trainers.
Wearing a helmet is obviously a legal requirement however there is no similar obligation to wear specific motorcycle boots. If the other side are using your clothing choices as a reason to pay out less, then it is up to them to prove that your injuries could have been reduced had you been wearing what they consider to be reasonable footwear by asking the medical expert his or her opinion on this point.
If you can prove that you were wearing reasonable footwear and you would have sustained the same injuries wearing motorcycle boots anyway, the insurers will not succeed.