Permissible radiation flux ( which can be obtained from Operating Company standards or from the relevant API) will be different depending on the cause of the flaring event. So even if the design capacity is not exceeded, the permissible radiation flux rate at points of interest will depend on whether the cause of this new peak rate is the same as that for the design case. Also note the points of interest for the permissible flux rate may differ depending on the cause of flaring event.
Same goes for dispersion analysis.
The contractor has to provide suitable justification for not carrying out a radiation study, and it cannot be just a simple case of whether design case flare capacity is exceeded or not. Sometimes, operating philosophy may have also changed since 2017. Sometimes, new equipment may have been installed after 2017 which may see high radiation loads. Tread carefully.